Railway     Signaling 

In 

Theory    and    Practice 


By 

JAMES  BRANDT  LATIMER 

SIGNAL  ENGINEER 

CHICAGO,  BURLINGTON  &  QUINCY 

RAILROAD 


OF   THE 

UNIVERSITY 

OF 

•0 


1909 

MACKENZIE-KLINK  PUBLISHING  COMPANY 
CHICAGO 


COPYRIGHT,  1909 

BY 
MACKENZIE-KLINK   PUBLISHING  COMPANY 


OF    THE 

UNIVERSITY 

OF 


TO  THE  SIGNAL  ENGINEERS 

OF    AMERICA    THIS    BOOK    IS    RESPECTFULLY    DEDICATED 
BY  ITS  AUTHOR. 


20l33o 


AUTHOR'S  PREFACE. 

In  the  ensuing  pages,  it  has  not  been  my  intention 
to  treat  the  subject  of  railway  signaling  as  practiced 
in  America  in  anything  but  an  elementary  way.  Even 
the  elements  are  not  always  readily  grasped  by  persons 
who  have  not  had  some  practical  railway  experience, 
and  are  at  least  somewhat  familiar  with  the  ordinary 
methods  pursued  in  constructing  tracks,  moving  trains 
and  in  the  nomenclature  used  by  those  whose  daily  life 
is  spent  in  actual  railway  operation. 

My  object  has  been  to  supply  a  want  which  I  myself 
felt  sorely  at  the  beginning  of  my  career  as  a  Signal 
Engineer — that  of  an  elementary  text  book  bearing  on 
the  subject. 

The  matter  was  originally  compiled  with  a  view  to 
publishing  it  serially,  and  indeed  nearly  one-half  of  it 
has  already  appeared  in  that  way.  Although  I  have 
taken  as  much  time  as  it  was  possible  for  me  to  spare 
from  a  busy  life  to  arrange  and  revise  the  matter  in 
proper  form  for  its  present  appearance,  I  cannot  but 
feel  that  I  may  have  left  a  great  deal  yet  to  be  done. 
I  can  only  say  that  I  have  tried  to  do  my  best  and  that 
I  hope  the  book  will  be  well  enough  received  to  give 
me  a  chance  to  make  any  revisions  which  may  appear 
advisable  in  a  later  edition. 

I  have  taken  the  liberty  fully  to  express  my  own 
opinions  where  I  have  thought  necessary,  and  have 
always  endeavored  to  impress  on  the  reader's  mind 
that  they  were  such  so  that  he  could  take  them  for 
what  they  are  worth. 

4 


PREFACE.  5 

After  more  than  eighteen  years  spent  in  the  operat- 
ing department  of  a  large  railroad,  and  nearly  seven 
years  as  its  Signal  Engineer,  I  cannot  but  feel  that 
these  opinions  must  be  worth  something  now  if  they 
ever  will  be.  The  reader  must  judge  for  himself. 

I  wish  to  take  this  opportunity  of  acknowledging 
much  valuable  assistance  in  collecting  matter  and 
preparing  illustrations  rendered  me  in  this  work  by 
Messrs.  Theodore  C.  Seifert,  Frank  Lyman  Beck- 
with,  Charles  W.  Breed,  and  Wm.  F.  Zane. 

I  shall  be  glad  at  any  time  to  receive  suggestions 
from  any  reader  for  the  improvement  of  the  book. 

JAMES  BRANDT  LATIMER. 
1404  East  Fifty-sixth  Street,  Chicago,  111. 
October  i,  1909. 


CONTENTS 

Page 

I.     INTRODUCTORY   7 

II.     GENERAL    16 

III.     INTERLOCKING — MECHANICAL   35 

v/    TV.     INTERLOCKING — POWER   56 

V.     LEADOUTS  AND  GROUND  CONNECTIONS.  .     66 
VI.     COMPENSATION  —  OFFSETS  —  FOUNDA- 
TIONS       81 

VII.     LOCKING  AND  OPERATING  DEVICES 91 

VIII.     SIGNALS  —  BOLT  LOCKS  —  SELECTORS — 

MECHANICAL  SLOTS 101 

•»/         IX.     DERAILS  —  GENERAL  REMARKS  ON  ME- 
CHANICAL INTERLOCKING  119 

X.     POWER  INTERLOCKING 131 

XL     ELECTRO-PNEUMATIC  INTERLOCKING.  ...   139 
XII.     ELECTRO-PNEUMATIC  INTERLOCKING 

CONTINUED    149 

XIII.  Low  PRESSURE  PNEUMATIC  INTERLOCK- 

ING     167 

XIV.  ALL  ELECTRIC  INTERLOCKING  GENERAL 

RAILWAY  SIGNAL  COMPANY'S  TYPE.  .   174 
XV.     OTHER  TYPES  OF  POWER  INTERLOCKING  192 

XVI.     LOCKING  AND  DOG  SHEETS 212 

XVII.  POWER  DISTANT  SIGNALS  —  CROSSING 
BARS — TIME  LOCKS — ELECTRIC  LOCK- 
ING— SWITCH  PROTECTION  SIGNALS.  .  247 
XVIII.  NIGHT  INDICATIONS — MANUAL  BLOCK- 
ING —  CONTROLLED  MANUAL  BLOCK- 
ING— ELECTRIC  SLOTS  272 

XIX.     AUTOMATIC    SIGNALS — AUTOMATIC     ^ 

TRAIN  STOPS 294 

XX.     JOINT  WORK  —  CONTRACTS  —  PUBLIC 

AUTHORITIES — ESTIMATES    318 

XXI.     CONCLUSION    343 

APPENDIX 359 

INDEX   417 


CHAPTER  I. 

INTRODUCTORY. 

Webster  defines  the  word  signal  as  meaning, 
"A  sign  used  for  the  purpose  of  giving  notice  to 
a  person  of  some  occurence,  command,  or  danger." 

As  applied  to  railroad  operating  practice,  this 
definition  appears  to  cover  the  ground  completely. 

Broadly  speaking,  railway  signals  may  be  divided 
into  two  grand  divisions :  Fixed  signals,  in  which 
is  included  any  form  of  signal  permanently  placed 
in  one  spot — as  semaphores,  switch  targets,  whistle 
boards,  etc. 

Other  signals,  in  which  is  included  any  form  of 
signal  not  of  a  permanent  nature,  as  a  flag  or  lamp 
in  the  hands  of  a  flagman,  or  a  torpedo  placed  on 
the  rail  to  warn  engine  runners  of  temporary  dan- 
ger. 

Engineering  practice  in  connection  with  signals 
may  be  said  to  be  confined  to  fixed  signals  only, 
although  the  drawing  up  of  specifications  for  colored 
bunting  for  flags,  and  for  colored  glass  for  lamp 
globes  and  lenses,  and  the  testing  of  such  articles 
after  purchase  would,  and  most  frequently  does, 
fall  upon  one  branch  or  another  of  the  engineering 
department. 

I  shall,  however,  confine  my  further  remarks  to 
fixed  signals  only. 

This  class  may  again  be  sub-divided  into  two 
other  classes,  visible  and  audible. 

7 


8  RAILWAY  SIGNALING 

In  the  former  class  would  be  included  sema- 
phores, switch  targets,  and  the  like,  with  their  lamps 
at  night,  and  in  the  latter  class,  highway  crossing 
alarms,  annunciators  to  warn  levermen  or  others  of 
the  approach  of  trains,  and  torpedoes  placed  by  tor- 
pedo machines. 

In  American  practice  little,  if  any,  general  use  is 
made  of  the  audible  fixed  signal  as  a  means  of  con- 
veying information  to  those  employed  in  running 
engines.  The  torpedo  machine  has  a  limited  use 
as  an  auxiliary  to  call  the  attention  of  enginemen 
to  the  fact  that  they  have  disregarded  a  visual  sig- 
nal, and  at  some  stations  trains  are  started  by  gongs 
or  fixed  whistles,  but  these  cases  are  more  often  the 
exception  than  the  rule. 

Visual  fixed  signals  may  again  be  sub-divided 
into  two  classes :  those  which  change  their  aspect 
and  those  which  do  not. 

The  former  class  would  include  semaphores,  disc 
signals,  switch  lights,  etc.,  and  the  latter  class, 
whistling  boards,  slow  signs,  water  tank  signs,  etc., 
etc. 

From  this  on  I  shall  omit  reference  to  this  latter 
class. 

The  former  class  may  again  be  divided  into 
three  minor  classes : 

(1)  Those  which  indicate  routes,  the  position  of 
switches,  etc. 

(2)  Block  signals. 

(3)  Train  order  signals. 

For  the  purpose  of  elementary  instruction,  this 
classification  cannot  be  too  strongly  impressed  on 
the  student's  mind. 

Under  No.  1  we  should  consider  signals  at  inter- 
locking plants,  switch  targets,  and  any  one  of  the 
myriad  types  of  signals  used  for  drawbridge  and  cross- 


IN  THEORY  AND  PEACTICE.  £ 

ing  protection  when  interlocking  is  not  used.  For 
interlocking  purposes  the  semaphore  signal,  Fig. 
i,  is  in  almost  universal  use. 

It  is  generally  used  for  two  purposes,  called  (1) 
the  home  signal,  (2)  the  distant  signal.  The  home 
signal  is  that  which  really  gives  the  indication  by 
which  the  engine  runner  is  governed.  The  distant 
signal  is  used  simply  to  forewarn  him  of  the  position 
of  a  home  signal.  Until  recently  the  almost  uni- 
versal practice  was  to  have  home  signal  blades 


Fig.  1. 

square  ended,  and  distant  signal  blades  with  a 
crotched  or  fish-tail  end,  Fig.  I.  Most  generally  the 
home  signal  blades  were  painted  red  and  the  distant 
signal  blades  green. 

It  is  regrettable  that  there  is  not  the  uniformity 
in  this  which  could  be  wished  for.  Some  years  ago 
the  Pennsylvania  Railroad,  using  the  argument  that, 
as  a  semaphore  blade  retained  its  color  always,  and 
that  it  was  bad  practice  to  allow  engine  runners 
to  pass  a  red  signal  under  any  circumstances,  de- 
cided to  paint  all  its  blades,  both  home  and  distant, 


10  RAILWAY  SIGNALING 

yellow,  and  to  depend  on  their  shape  to  distinguish 
one  from  the  other.  Later  several  other  companies 
adopted  this  system.  The  more  general  practice, 
however,  has  been  to  retain  red  for  the  home  signal 
blade. 

As  the  semaphore  is  purely  a  position  signal  and 
the  color  has  nothing  to  do  with  the  indication  it  is 
intended  to  give,  I  have  always  thought  that  we 
might  as  well,  for  the  sake  of  uniformity,  all  adopt 
the  Pennsylvania  plan,  but,  so  far,  little  or  nothing 
has  been  done  along  that  line,  excepting  by  roads 
more  or  less  closely  connected  with  the  Pennsyl- 
vania. 

During  the  last  few  years  there  has  been  a  strong 
movement  in  favor  of  doing  away  with  the  so- 
called  white  light  for  a  clear  indication  at  night, 
and  substituting  therefor  a  green  light.  On  roads 
which  have  made  this  change,  in  most  cases  an 
orange-yellow-  light  is  used  for  caution,  and  distant 
signal  blades  have  been  painted  yellow.  •> 

The  Chicago  &  North- Western  is  an  exception. 
That  company  adopted  a  green  light  for  clear  sev- 
eral years  ago,  and  uses  a  red  and  green  light  side 
by  side  as  its  caution  indication. 

Generally  speaking,  a  home  semaphore  blade  in 
the  horizontal  position  means  "stop/'  while  a  dis- 
tant semaphore  blade  in  the  horizontal  position 
means  "caution,"  or  proceed  slowly,  expecting  to 
find  the  home  signal  at  stop. 

Of  late  years  there  has  been  a  movement  led  by 
the  Pennsylvania  to  have  three  positions  for  the 
semaphore  blade: 

Horizontal— "Stop." 

Inclined  at  an  angle  of  45  degrees — "Caution." 

Vertical— "All  clear— proceed." 

These  indications  may  be  given  either  in  the 
upper  or  lower  right  hand  quadrant  of  the  circle 


IN  THEORY  AND  PRACTICE.  11 

which  the  blade  would  describe  with  its  free  end  if 
revolved  on  the  pivot  holding  the  fixed  end. 

Some  few  installations  have  been  made  where 
the  upper  right  hand  quadrant  is  used,  mostly  within 
the  last  few  months.  With  the  three  position  sig- 
nals it  is  possible  to  carry  the  principle  of  position 
governing  to  a  logical  issue,  as  the  distant  sema- 
phore has  only  the  caution  (inclined  at  45  degrees) 
and  clear  (vertical)  positions  while  the  home  sig- 
nal has  only  the  stop  (horizontal)  and  clear  posi- 
tions. 

The  student  should  thoroughly  understand  what 
a  good  many  signal  men  do  not  appear  to  grasp, 
that  the  blade  of  a  semaphore  is  the  signal.  Two 
or  even  three  blades  are  frequently  put  on  one  mast, 
but  each  is  a  separate  signal. 

As  regards  interlocking,  I  shall  say  little  here,  as 
I  could  not  go  into  the  subject  in  any  detail  without 
going  far  beyond  the  limits  of  this  introductory 
chapter.  But  later  on  I  will  endeavor  to  treat  it  as 
fully  as  it  is  desirable.  Suffice  it  to  say  that  by  the 
interlocking  arrangement  the  switches  and  signals 
can  only  be  moved  in  such  a  way  that  a  train  is 
insured  a  safe  passage  over  some  dangerous  place 
like  a  switch,  drawbridge,  crossing  or  junction  if 
the  signals  authorizing  it  to  proceed  are  so  dis- 
played. 

The  designing  of  interlocking  is  the  most  import- 
ant and  also  the  most  difficult  to  acquire  of  any 
part  of  a  signal  engineer's  duty,  and  any  person  con- 
templating the  taking  up  of  signal  engineering  should 
make  a  special  study  of  this. 

I  will  say,  before  passing  on,  that  the  switches, 
signals,  etc.,  controlled  by  an  interlocking  plant, 
may  be  moved  by  manual  power,  compressed  air  or 
electricity,  but  the  principles  of  the  interlocking  are 
always  the  same.  An  interlocking  plant  is  always 


12  RAILWAY  SIGNALING 

controlled  by  an  operator,  or  leverman,  as  he  is 
generally  called.  There  are  no  automatic  inter- 
lockings. 

Route  signals  other  than  semaphores,  such  as  switch 
targets  and  lamps,  are  of  so  many  designs  that  they 
cannot  be  described.  It  may  safely  be  said  that  they 
are  all  crude  and  that  there  is  no  reason,  except 
the  expense,  why  semaphores  cannot  be  used,  for 
all  purposes  where  fixed  visual  signals  are  required, 
thereby  at  one  step  doing  more  to  standardize  signal 
practice  in  the  United  States  than  has  ever  been  done 
before. 

"  'Tis  a  consummation  devoutly  to  be  wished." 

We  will  now  consider  block  signals.  To  the 
public  this  name  means  everything.  To  the  signal 
engineer  it  means  simply  the  signal  which  tells  an 
engine  runner  whether  or  not  he  may  proceed  into  a 
block.  The  reader  is  doubtless  familiar  with  the 
definition  of  a  block,  so  I  shall  not  take  space  to 
explain  it. 

Block  signals  are  of  two  general  types: 

Manual:  Those  which  are  operated  by  a  person 
whose  duty  it  is  to  do  so. 

Automatic:  Those  which  are  operated  automatic- 
ally by  the  train  itself. 

In  all  cases  semaphore  signals  may  and  ought  to 
be  used  for  block  signals,  though  the  first  form  of 
automatic  signal  was  a  disc,  and  many  of  them  are 
still  in  service. 

Where  manual  block  signals  are  used,  the  block 
operators  are  stationed  at  convenient  places  along 
the  line  to  operate  them.  Each  man  communicates 
with  the  operators  at  the  other  end  of  the  two 
blocks  adjacent  by  telegraph,  telephone  or  in  some 
cases  by  bells. 

Frequently  an  arrangement  is  made  by  which 
each  operator,  by  the  act  of  clearing  his  signal, 


IN  THEORY  AND  PRACTICE.  13 

electrically  locks  the  signal  at  the  other  end  of  the 
block  in  the  stop  position.  This  is  then  called 
controlled  manual  block,  and  sometimes  it  is  so 
arranged  that  the  train  automatically  sets  the  sig- 
nal at  danger  behind  it  and  holds  it.  at  danger 
during  its  passage  through  the  block,  and  it  takes 
the  operator's  action  to  again  clear  the  signal  for 
another  train  after  the  first  one  has  passed  out  of 
the  block.  This  is  the  semi-automatic  block,  and, 
in  my  opinion,  is  the  best  and  safest. 

There  is  a  type  of  manually  controlled  block 
known  as  the  "staff  system,"  of  which  a  more 
detailed  description  will  be  given  later.  It  is  in 
reality  a  development  of  the  first  crude  method 
of  blocking  trains  and  has  stood  the  test  of  seventy 
years'  service  in  Great  Britain,  where  it  is  in  general 
use  on  single  track  lines,  but  in  the  United  States 
there  are  few  installations. 

Automatic  block  signals  are  all  operated  by  a 
track  circuit.  The  track  circuit  is  simple  and  will 
be  explained  in  detail  further  on. 

Suffice  it  to  say  here  that  a  section  of  track  of 
suitable  length  (this  to  be  determined  by  conditions 
of  ballast,  etc.),  ranging  usually  from  2,500  to  5,000 
feet,  is  electrically  separated  from  the  track  on 
each  side  of  it  by  putting  rail  joints,  which  are 
insulated  with  fiber,  on  each  end  of  the  rails  on 
either  side.  The  rails  in  the  section  are  bonded 
together  by  wires  (usually  J>No.  8  (galvanized), 
riveted  into  the  ends  of  the  rails  so  as  to  make 
a  continuous  path  for  the  electric  current.  A  bat- 
tery, usually  two  cells  of  gravity,  is  connected  to 
one  end  of  the  section,  one  pole  to  the  rail  on  one 
side,  and  one  pole  to  the  rail  on  the  other.  In  this 
condition  no  current  flows  as  there  is  no  connection 
between  the  rails.  At  the  other  end  of  the  section, 
therefore,  a  low  resistance  (usually  4  ohm)  relay 


14  RAILWAY  SIGNALING 

is  connected  to  the  rails  so  that  the  current  from  the 
battery  flows  through  it. 

Now  if  a  pair  of  wheels  enters  this  section  of 
track  the  current  of  the  battery,  taking  the  path  of 
least  resistance,  crosses  from  one  rail  to  the  other 
through  the  axle  instead  of  the  relay,  and  leaves  the 
relay  unenergized.  Its  armature  falls  back  by 
gravity,  thereby  making  or  breaking  a  local  circuit 
which  operates  the  signal,  or  in  some  cases  opening 
a  valve  which  admits  compressed  air  or  gas  under 
pressure  to  a  cylinder  which  operates  the  signal. 

There  are  hundreds  of  signal  circuits,  but  the 
track  circuit  is  always  the  same. 

I  will  not  discuss  the  difference  between  normal 
clear  and  normal  danger  automatic  block  signals, 
further  than  to  say  that  in  the  former  the  signal 
is  normally  at  clear  and  goes  to  danger  as  a  train 
passes  it,  while  in  the  latter  the  signal  stands  nor- 
mally at  danger,  and  goes  to  clear  if  the  block  which 
it  governs  is  clear  as  a  train  approaches  it,  and  to 
danger  after  the  train  has  passed  it.  Each  system  has 
its  adherents.  The  normal  clear  seems  to  have  the 
best  of  it  now. 

Train  order  signals  frequently  are,  and  always 
should  be,  though  in  old  installations  many  forms 
of  discs  were  used,  of  the  semaphore  type.  They 
are  used  to  advise  engine  runners  when  dispatcher's 
orders  are  to  be  given  them.  They  are  always 
manual  signals  to  be  operated  by  the  telegraph 
operator  who  takes  the  train  order. 

Where  manual  blocking  is  done,  they  (the  train 
order  signals)  are  used  as  block  signals  also  in 
most  cases. 

One  word  about  night  indications.  In  all  cases 
a  red  light  means  stop.  Where  a  white  light  is 
used  for  clear,  green  is  used  for  caution,  but  where 


IN  THEOET  AND  PRACTICE.  15 

green  is  used  for  clear,  as  explained  earlier,  either 
yellow,  or  red  and  green  together,  means  caution. 

It  is  good  practice,  and  frequently  done,  to  use 
distant  signals  with  block  or  train  order  signals 
as  well  as  with  route  home  signals. 

So  much  for  an  introduction  to  a  more  detailed 
description  of  each  of  the  general  heads  mentioned, 
which  we  will  now  proceed  to  place  before  the  reader. 


CHAPTER  II. 

GENERAL. 

A  word  may  as  well  be  said  here  with  reference  to 
the  plans  or  drawings  used  by  signal  engineers. 

At  the  present  time  I  shall  not  give  a  complete 
list  of  the  conventional  signs  used  by  signal  drafts- 
men to  designate  the  various  apparatus.  The  Rail- 
way Signal  Association  and  the  Engineering  and 
Maintenance  of  Way  Association  have  adopted  a 
set  of  conventional  signs,  which  has  been  issued  in 
pamphlet  form  by  several  of  the  leading  signal 
companies,  and  is  procurable  from  them,  but  as 
we  advance  the  signs  called  into  use  by  each  step 
will  be  explained  and  used  thereafter  in  this  work. 

As  a  rule  it  will  be  found  that  track  plans  drawn 
to  a  scale  of  one  inch  on  the  plan  equals  one  hun- 
dred feet  on  the  ground  are  of  a  very  convenient 
form.  On  some  drawings  requiring  a  great  deal 
of  detail  a  scale  of  one  inch  on  the  plan  equals 
fifty  feet  on  the  ground  may  be  found  convenient. 
Scales  such  as  one  inch  equals  twenty  or  thirty 
feet  are  not  to  be  recommended.  As  will  be  ex- 
plained later,  plans  for  long  stretches  of  track  show- 
ing a  block  signal  arrangement  may  with  propriety  be 
drawn  to  a  much  smaller  scale,  one  inch  equals  a 
thousand  feet  or  even  a  mile,  for  instance,  but  the 
branch  of  our  subject  now  before  us  is  route  sig- 
naling, so  that  we  will  confine  our  present  remarks 
to  the  plans  used  therewith.  These  plans,  as  be- 
fore stated,  can  generally  be  drawn  to  a  scale  of 

16  V 


IN  THEORY  AND  PRACTICE. 


17 


i"=ioo  feet,  and  in  exceptional  cases  of  i"  =  5o 
feet. 

In  designing  the  route  signaling  for  any  given 
point  the  signal  engineer  first  draws  up  his  "track 
plan,"  which  is  merely  a  map  of  the  locality  where 
the  signals  are  to  be  placed,  drawn  to  the  accepted 
scale,  and  showing  all  the  tracks,  switches,  cross- 
ings, etc.,  in  the  vicinity.  It  is  not  desirable  to 
go  into  topographical  details.  In  fact,  all  cuts,  tun- 
nels, bridges,  culverts  and  buildings  that  do  not 
have  a  direct  influence  on  the  construction  of  the 


Fig.  2. 

signaling  apparatus  had  better  be  omitted,  as  show- 
ing them  on  the  plan  serves  only  to  complicate  it, 
and  requires  an  unnecessary  expenditure  of  the 
draftsman's  labor.  Water  cranes  and  water  tanks, 
coal  chutes,  station  buildings  and  platforms  had,  as  a 
general  thing,  better  be  shown. 

Fig.  2  shows  a  double  track  line  crossed  by  a 
single  track  line,  a  crossover  between  the  two  tracks 
of  the  double  track  line  and  a  junction  of  a  single 
track  line  all  drawn  originally  to  a  scale  of  one  inch 
equals  one  hundred  feet,  with  a  tunnel,  a  bridge,  an 


18  RAILWAY  SIGNALING 

overhead  bridge,  a  highway  crossing,  a  drawbridge  and 
a  lift  bridge,  all  shown  in  the  conventional  way  as 
recommended  by  the  Railway  Signal  Association 
and  the  Engineering  and  Maintenance  of  Way  As- 
sociation. In  addition  thereto,  it  may  be  noted 
that  a  semaphore  signal  is  shown  at  "a,"  also  in 
the  conventional  manner.  The  arrow  just  to  the 
right  of  "a"  indicates  the  normal  direction  of  traffic 
(the  direction  in  which  trains  are  supposed  to  run) 
on  the  track  shown  as  A  B.  It  should  here  be 
thoroughly  grasped  by  the  student  that  the  con- 
ventional manner  of  showing  a  semaphore  on  a 
track  plan  is  as  if  it  was  laid  down  on  the  ground 
with  its  base  towards  a  train  approaching  it  in  the 
normal  direction  of  traffic,  or  in  the  case  of  a  single 
track  line,  in  the  direction  in  which  a  train  ap- 
proaching the  signal  from  its  front  would  be  mov- 
ing, and  its  top  (that  end  nearest  which  the  blade 
is  placed)  away  from  an  approaching  train.  The  dis- 
tinction between  the  front  and  the  back  of  a  semaphore 
will  be  explained  more  fully  further  on. 

I  have  noticed  that  a  great  many  persons,  some 
of  them  competent  engineers,  overlook  this  fact 
and  draw  semaphore  signals  just  the  opposite  way, 
which,  being  contrary  to  accepted  practice,  is 
wrong  and  can  only  expose  the  person  who  does 
it  to  ridicule  or  perhaps  do  him  an  injustice  by 
giving  an  impression  to  a  better  informed  person 
that  he  is  entirely  ignorant  of  the  subject  of  railroad 
signaling,  when  in  reality  he  may  be  well  informed 
except  on  this  one  point. 

Besides  the  distinction  already  referred  to  be- 
tween a  home  and  a  distant  semaphore  signal 
there  is  yet  another  type  of  semaphore  known  as 
a  dwarf  signal.  This  is  used  always  as  a  home 
signal.  It  is  like  a  home  semaphore  signal  in 
miniature  when  operated  by  manual  power;  when 


IN  THEORY  AND  PRACTICE. 


19 


operated  by  other  power  such  as  electricity  or  com- 
pressed air,  the  operating  mechanism  which  is 
usually  placed  in  a  case  which  also  serves  as  a  post 
to  support  the  blade,  occupies  so  much  room  that 
it  requires  a  considerable  stretch  of  the  imagin- 
ation to  detect  the  resemblance  between  this  signal 
and  a  high  semaphore. 

Where  it  is  advisable  to  have  a  high  and  a 
dwarf  signal  close  together  the  saving  of  a  separate 
post  or  mast,  as  it  is  generally  called,  for  the  dwarf 
signal  is  frequently  effected  by  attaching  a  small 
blade  to  the  mast  of  the  high  semaphore  signal. 
When  this  is  done  this  blade  is  usually  placed  ten 


Fig.  3. 

feet  above  the  ground.  The  lowest  blade  of  a  high 
semaphore  is  placed  twenty-;five  feet  above  the 
ground.  Where  a  separate  mast  is  used  for  a 
dwarf  signal  it  is  rarely  more  than  three  feet  high. 
Fig.  3  shows,  a,  a  mechanically  operated  dwarf 
signal,  b,  an  electrically  operated  dwarf  signal, 
c,  a  pneumatically  operated  dwarf  signal,  and,  d, 
Fig  3a,  a  high  mechanical  semaphore  signal  with  small 
low  blade  in  lieu  of  a  separate  dwarf  signal. 
High  semaphore  signals,  both  home  and  distant, 
dwarf  signals,  and  an  innumerable  variety  of  discs, 


20 


EAILWAT  SIGNALING 


Flg.Sa. 


targets,  etc.,  are  used 
as  route  signals,  the 
latter  principally  on 
switch  stands,  but 
sometimes  in  old  in- 
stallations to  govern 
the  movements  of 
trains  over  crossings 
and  drawbridges. 

I  shall  now  discuss 
the  use  of  semaphores 
as  route  signals  and 
say  a  few  words  later 
about  the  other  types. 

Turning  again  to 
Fig.  2  the  reader  will 
see  that  on  the  right- 
hand  side,  facing  in 
the  direction  of  traffic, 
of  track  C  D  to  the  left 
of  the  junction  switch 
I  have  shown  a  sema- 
phore with  two  blades. 
This  is  to  govern  the 
two  routes  which  may 
be  given  by  the  junc- 
tion switch.  When  a 
two  -  bladed  semaphore 
is  used  it  is  the  ac- 
cepted practice  that  the 
upper  blade  governs 
the  superior  and  the 
lower  blade  the  inferior 
route,  but  the  distinc- 
tion between  the  supe- 
rior and  inferior  routes 
may  be  a  purely  arbi- 


IN  THEORY  AXD  PRACTICE.  21 

trary  one  where,  as  in  the  case  of  a  junction  on  either 
line  of  which  the  traffic  is  of  about  the  same  kind  and 
importance,  it  would  be  a  difficult  matter  to  decide 
which  of  the  two  lines  was  the  more  important. 

Generally,  if  one  line  is  straight  and  the  other 
diverges  from  it  by  an  ordinary  turnout,  as  in  the 
case  of  the  single  track  line  shown  in  the  figure, 
the  straight  line  is  considered  the  superior  route, 
and  I  shall  so  consider  it  here.  If,  therefore,  a  train 
is  moving  from  C  towards  D  and  the  upper  blade 
of  this  signal  is  at  clear,  the  engine  runner  of  the 
train  knows  upon  coming  in  view  of  this  signal  that 
the  person  controlling  it  intends  him  to  proceed  on 
this  route,  and  it  is,  therefore,  unnecessary  for  him 
to  slacken  speed,  and,  as  it  were,  feel  his  way,  as  he 
would  be  forced  to  do  if  there  was  no  signal  to  give 
him  this  information. 

If,  on  the  contrary,  this  same  engine  runner  finds 
the  upper  blade  in  the  stop  position,  but  the  lower 
blade  clear,  he  will  know  at  a  glance  that  he  can- 
not take  the  route  to  D,  and  must,  if  he  proceeds, 
take  the  diverging  route  to  E.  If,  of  course,  he 
knows  that  he  cannot  reach  his  destination  by  tak- 
ing the  route  to  E,  he  will  know  that  this  route 
is  not  intended  for  his  train,  but  that  the  person 
controlling  the  signal  has  probably  mistaken  his 
train  for  another  which  should  be  sent  forward  via 
route  to  E,  and  will  stop  his  train  and  have  the 
route  changed  before  proceeding,  even  though  the 
signal  has  shown  him  that  he  may  proceed  with 
safety  towards  E. 

If,  however,  he  finds  both  blades  in  the  stop 
position  he  perceives  that  the  person  controlling  the 
signal  does  not  wish  him  to  proceed  by  either  route, 
and  that  he  must  consequently  stop  and  wait  until 
the  proper  signal  is  cleared. 


22  MAILWAY  SIGNALING 

These  three  cases  cover  all  the  information  that 
can  be  given  by  a  two-position  home  route  signal, 
viz. — proceed  by  the  superior  route — proceed  by  an 
inferior  route — stop.  I  would  call  the  reader's 
particular  attention  to  the  wording  of  the  second 
case.  There  I  have  said  "proceed  by  an  inferior 
route."  In  early  installations  in  this  country  it 
was  not  uncommon  to  have  three  or  even  four 
high  signals  on  one  mast,  and  although  it  is  not 
now  considered  good  practice  to  display  more  than 
two,  the  lower  one  may  govern  more  than  one 
route.  Cases  where  it  is  necessary  to  govern  two 
or  more  important  routes  by  one  signal  do  not 
occur  often,  and  can  quite  generally  be  avoided  by 
the  use  of  an  extra  signal. 

Careful  experiments  made  at  various  times  have 
proved  beyond  doubt  that  even  with  the  improved 
train  brakes  used  on  railway  equipment  it  is  not  ad- 
visable to  consider  that  the  heavy  trains  now  being 
run  at  high  speeds  can  be  stopped  on  an  average  in 
less  than  2,500  feet  from  the  time  the  brakes  are 
applied. 

In  the  case  of  route  signals  giving  the  stop  in- 
dication it  is  necessary  that  an  engine  runner  should 
stop  his  train  before  passing  them,  so  that,  for  one 
reason,  they  will  be  within  his  range  of  vision 
when  they  are  changed  to  the  proceed  position. 
Permanent,  natural  or  artificial  conditions,  such 
as  woods,  hills,  buildings,  etc.,  may  render  it  im- 
possible for  an  engine  runner  to  see  a  home  signal 
2,500  feet  before  reaching  it,  and  temporary  con- 
ditions, such  as  rain,  snow  or  fog,  may  occur  with 
the  same  result  at  any  time.  In  order,  therefore, 
to  enable  an  engine  runner  to  get  his  train  under 
such  control  that  he  can  stop  before  overrunning 
a  stop  signal,  distant  signals  as  shown  at  "c"  in 
the  figure  are  provided.  It  is  good  practice  and 


IN  THEORY  AND  PRACTICE.  23 

at  present  is  being-  quite  generally  done  to  provide 
a  distant  signal  for  each  high  home  signal,  although 
formerly  it  was  the  more  general  custom  to  pro- 
vide only  one  distant  signal  which  repeated  the 
superior  route  home  signal  and  stood  at  caution 
when  the  inferior  route  home  signal  was  cleared. 
The  assumption  being-  that  the  inferior  route  being 
a  diverging  one,  as  it  is  in  most  cases,  should  be 
taken  slowly  anyway,  and  that  an  engine  runner 
coming  up  to  a  distant  signal  at  caution  would 
put  his  train  under  control  in  preparation  for  a 
stop  at  the  home  signal,  which  would  insure  that 
he  would  then  take  the  turnout  at  reduced  speed, 
while  on  the  other  hand,  if  he  was  given  a  clear  dis- 
tant signal,  showing  that  the  route,  even  though  the 
inferior  one  was  clear,  he  might  not  slow  down, 
and  would  take  the  turnout  at  a  higher  rate  of  speed 
than  would  be  safe. 

At  the  present  time  when  frogs  of  as  acute  an 
angle  as  No.  24  are  in  common  use  in  main  line 
turnouts,  this  objection  to  a  distant  signal  for  each 
home  signal  ceases  to  be  such  a  cogent  one,  and, 
as  before  stated,  the  best  practice  nowadays  is  to 
provide  the  additional  distant  signal. 

The  reader  should  note  that  in  speaking  of  a 
distant  signal  I  have  used  the  word  caution  posi- 
tion. A  distant  signal  proper  has  but  two  posi- 
tions, caution  and  proceed.  In  the  original  two- 
position  signal  systems  in  the  caution  position  the 
blade  of  the  distant  signal  was  horizontal,  which 
was  the  same  position  as  the  stop  of  the  home 
signal,  the  distant  signal  being  distinguished  from 
the  home  by  its  color  and  shape — usually  having 
a  V-shaped  notch  cut  in  its  end.  This  has  led 
a  great  many  people  who  should  really  know  better 
to  carelessly  speak  of  a  distant  signal  in  the  stop 
position,  an  inaccuracy  which  should  be  carefully 


24  RAILWAY  SIGNALING 

avoided,  as  it  is  very  confusing  to  people  who  are 
not  thoroughly  familiar  with  the  terms  used  and 
uses  of  the  various  signals. 

A  home  signal  in  a  two-position  system  has  but 
two  positions — stop  and  proceed — but  in  a  three^ 
position  system  it  has  three  positions — stop,  proceed 
cautiously  and  proceed  without  limitation.  This  will 
be  gone  into  more  fully  later.  At  present  we  shall 
confine  ourselves  to  two  position  signals. 

We  next  come  to  the  use  of  dwarf  signals.  Un- 
fortunately there  is  not  the  same  uniformity  of  prac- 
tice with  their  use  as  there  is  with  high  signals, 
some  signal  engineers  preferring  to  use  high  sig- 
nals where  others  use  dwarf  signals.  It  may  gen- 
erally be  said  that  dwarf  signals  are  always  used 
for  reverse  or  back-up  movements  on  main  tracks. 
That  is,  on  a  double  track  line  where  it  is  neces- 
sary, as  at  a  crossing,  to  have  a  signal  which  would 
only  govern  a  train  backing  up  or  moving  in  the 
direction  opposite  to  the  normal  direction  of  traffic 
on  that  track,  a  dwarf  signal  would  be  used.  Most 
generally,  too,  where  there  is  a  crossover  between 
two  main  tracks  the  route  through  it  is  governed  by 
a  dwarf  signal.  The  difference  of  opinion  has 
arisen  over  the  question  whether  it  is  better  to  govern 
the  routes  from  main  tracks  to  passing  tracks  or  yards 
with  dwarf  or  high  signals. 

It  should  be  here  understood  that  the  use  of  a 
dwarf  signal  in  the  particular  case  now  referred  to 
is  that  where  it  is  used  in  conjunction  with  a  high 
signal,  either  by  placing  a  small  blade  ten  feet 
from  the  ground  on  the  high  signal  mast  as  before 
described,  or  by  using  a  dwarf  signal  placed  at  the 
base  of  the  high  signal. 

Fig.  4  will  serve  to  illustrate  this.  A  train  mov- 
ing from  A  in  the  direction  of  the  arrow  would 
be  given  distant  signal  1  and  home  signal  2,  if 


IN  THEORY  AND  PRACTICE.  25 

it  was  to  continue  along  the  main  track  towards  B.  If, 
however,  it  was  to  take  the  siding,  distant  signal 
i  would  be  held  at  caution,  home  signal  2  at  stop 
and  dwarf  signal  3  would  be  cleared. 

Several  years  ago  when  signaling  in  this  country 
was  in  its  infancy  high  signals  were  more  fre- 
quently used  for  this  purpose.  As  railroad  signaling 
came  to  this  country  from  Europe  and  was  first 
applied  where  traffic  was  most  dense,  viz.,  in  the 
east,  eastern  signal  engineers  appear  to  have  be- 
come accustomed  to  the  use  of  the  high  signal.  In 
the  west,  where  the  whole  art  of  signaling  is  of 
much  more  recent  date,  the  dwarf  signal  appears  to 


Fig.  4. 

be  preferred.  My  own  preference  is  for  the  dwarf 
signal.  It  cannot  be  seen  from  any  great  distance, 
and  as  it  has  no  distant  signal  and  the  distant  signal 
for  the  high  home  signal  is  at  caution,  an  engine  run- 
ner on  coming  up  to  the  distant  signal,  being  unable 
to  see  the  dwarf,  must  get  his  train  under  control  and 
must  have  slowed  down  to  a  speed  with  which  he  may 
enter  the  turnout  with  safety  by  the  time  he  comes  in 
view  of  the  dwarf  signal. 

I  have  known  cases  where  the  signal  for  this 
move  has  been  given  by  a  lower  high  arm  which 
in  clear  weather  could  be  seen  from  the  distant 
signal  in  which  the  engine  runner,  seeing  this  lower 
arm  clear,  has  failed  to  slow  down  and  has  en- 
tered the  turnout  at  such  a  rate  of  speed  as  to 
cause  a  derailment.  These  turnouts  are  most  fre- 
quently taken  by  freight  trains  in  which  there  is 
always  likely  to  be  a  car  unevenly  loaded,  which 
increases  the  liability  of  its  being  derailed  when 


26  RAILWAY  SIGNALING 

suddenly  brought  into  the  sharp  curve  of  the  turn- 
out at  high  speed. 

For  fear  that  some  reader  may  be  misled  into 
believing  that  there  is  a  contradiction  between  the 
position  I  have  here  taken  in  regard  to  the  use  of 
distant  signals  (see  page  23)  and  in  regard  to  the 
use  of  dwarf  signals,  I  want  to  say  in  explanation 
that  the  two  cases  are  not  parallel.  What  I  said 
in  regard  to  the  distant  signal  referred  to  the  diver- 
gence of  two  or  more  high  speed  routes,  and  though 
one  is  designated  the  superior  and  the  other  the 
inferior,  they  are  all  constructed  in  such  a  manner 
that  trains  may  take  any  one  of  them  at  speed, 
but  in  the  case  of  the  side-track  movement,  where 
the  use  of  a  dwarf  signal  is  preferred,  the  route  is 
one  not  intended  for  fast  running.  The  frogs  of 
the  turnouts  are  anywhere  from  Nos.  8  to  12,  and 
the  track  beyond  is  generally  constructed  purely  for 
low  speed  use.  It  is,  however,  just  because  there 
is  an  apparent  similiarity  between  the  two  cases 
that  the  difference  of  opinion  as  to  the  use  of  the 
dwarf  signal  has  arisen. 

It  quite  frequently  occurs  that  there  are  two  or 
more  reverse  and  low  speed  routes  diverging  from 
points  so  close  together  that  one  dwarf  signal  can 
govern  them  all,  as  for  instance,  a  side  track  lead- 
ing from  one  track  of  a  double  track  line  by  a 
facing  point  switch  and  immediately  behind  its 
frog  a  facing  point  crossover  between  the  two  main 
tracks.  In  such  cases  it  is  the  more  general  prac- 
tice to  let  the  one  dwarf  signal  govern  both  routes. 
It  is,  however,  permissible,  and  in  some  cases  quite 
desirable,  to  have  two  blades  on  the  dwarf  mast. 
More  than  two  blades,  however,  should  never  be 
used. 

This  is  shown  in  Fig.  5. 

In  such  cases  there  is  no  fixed  rule  as  to  which 


IN  THEORY  AND  PEACT1CE.  27 

of  the  slow  routes  is  the  superior,  and  the  upper 
blade  may  govern  either  of  them,  at  the  option  of 
the  signal  engineer. 

Besides  the  semaphore  type  of  dwarf  signal  here- 
tofore referred  to  there  is  what  is  known  as  a  pot 
signal.  This  is  made  to  revolve  on  a  vertical  shaft 
like  a  switch  target,  and  is  generally  connected  di- 


Flg.  5. 

rectly  to  the  points  of  a  switch,  the  route  through 
which  it  governs,  or  at  least  to  the  locking  arrange- 
ment by  which  the  switch  is  held  in  position  after 
it  has  been  thrown. 

The  use  of  this  signal  nowadays  is  confined  to 
very  unimportant  tracks  where  cars  are  placed  to  be 
unloaded,  and  even  then  it  is  better  practice  to  use 
a  dwarf  signal  of  the  semaphore  type. 

We  now  come  to  the  use  of  three-position  signals 
for  route  signaling.  The  three-position  signal  is 
an  evolution  and  was  suggested  by  motives  of 
economy.  In  England,  where  semaphore  signals 
were  first  used  for  railroad  purposes,  the  two-posi- 
tion signal  is  the  universal  type.  There  semaphore 
signals  are  so  numerous  that  it  became  frequently 
advisable  to  place  the  distant  signal  for  one  home 
signal  on  the  same  mast  with  the  home  signal 
next  in  front  of  it,  as  shown  in  Fig.  6. 

Ui_^  IJi    ...  1J , 

Fig.  6. 

This  condition  exists  more  frequently  with  block 
signals  than  with  route  signals,  but  as  we  have  not 
yet  arrived  at  that  part  of  the  subject  we  will  as- 


28 


SAILWAY  SIGNALING 


sume  that  this  condition  applies  to  route  signals 
pure  and  simple. 

English  practice  at  first  ruled  in  this  country, 
but  later  some  American  signal  engineers  sug- 
gested an  arrangement  by  which  one  blade  could 
be  made  to  do  double  duty  and  act  both  as  a  home 
and  distant  signal.  This  was  accomplished  by 
having  the  blade  horizontal  as  at  a,  Fig.  7,  mean 


Fig.  7. 

stop,  inclined  downward  at  an  angle  of  45°  as  at 
b,  mean  proceed  cautiously,  and  vertically  down- 
ward as.  at  c  mean  proceed  without  limitation. 
This  effected  a  saving  of  a  blade  with  its  attach- 
ments and  lamp  for  each  mast  from  which  a  home 
and  distant  signal  had  been  displayed.  For  route 
signaling  proper,  such  as  we  are  now  discussing, 
the  need  for  such  an  arrangement  does  not  often 
occur,  yet  there  are  times  when  it  is  very  con- 
venient to  display  a  distant  signal  for  a  home  signal 
further  away  from  the  same  mast  as  a  home  signal. 
A  typical  case  of  this  is  shown  in  Fig.  8,  the 
upper  line  showing  how  it  would  be  done  in  a  two- 


IN  THEOEY  AND  PRACTICE.  29 

position  system,  and  the  lower  line  showing  the 
same  with  a  three-position  system. 

As  stated  earlier,  the  most  recent  suggestion  is 
to  give  the  indication  in  the  upper  quadrant  instead 
of  the  lower  one.  So  far  this  is  confined  to  a 
three  position  system,  although  there  is  no  reason 
that  it  could  not  be  applied  equally  as  well  to  a 
two-position  system. 

Undoubtedly  the  use  of  three-position  signals  has 
grown  in  favor  very  rapidly  during  the  past  five 
years,  yet  there  are  still  many  firm  supporters  of 
the  two-position  system,  who  advance  arguments  in 
support  thereof  well  worth  consideration.  It  would 
hardly  be  desirable  to  go  further  into  this  phase  of 


Trvir*  may  pass  Ibis  sicfno/  expecting  to  Find  nex 

Fig.  8. 

the  subject  at  the  present  time,  but  before  closing 
this  work  I  shall  endeavor  to  lay  before  the  reader 
both  sides  of  the  question  and  allow  him  to  form  his 
own  opinions. 

The  proper  placing  of  signals  is  a  very  important 
question  and  one  which  should  be  given  the  most 
careful  attention. 

Where  single  masts  are  used  they  should,  when- 
ever possible  to  do  so,  be  placed  on  the  right-hand 
side  of  the  track  they  govern,  and  the  blade  should 
always  extend  from  the  right-hand  side  of  the  mast, 
except  on  two  or  more  track  railroads,  where  trains, 
as  is  the  custom  in  England,  habitually  pass  each 
other  to  the  left,  when  the  mast  is  placed  on  the 
left-hand  side  of  the  track  it  governs,  with  the  blade 
extending  from  the  right  of  the  mast. 


30  RAILWAY  SIGNALING 

Happily  for  the  uniformity  of  American  signal 
practice  there  are  not  many  of  our  railroads  which 
run  "left-handed,"  and  one  at  least  of  the  most 
important  of  these  proposes  to  abandon  this  cus- 
tom in  the  near  future,  an  example  which  will  no 
doubt  soon  be  followed  by  others. 

The  distinction  between  the  right  and  left  hand 
of  a  track  is  made  as  follows: 

The  direction  of  traffic  on  a  double  track  line 
is  of  course  established.  If  a  person  stands  with  his 
back  towards  an  approaching  train  and  facing  in 
the  direction  the  train  is  moving  the  right  side  of 
the  track  will  be  that  on  his  right  hand,  just  as 
the  starboard  side  of  a  ship  is  the  right  side  to  a 
person  facing  the  bow. 

On  double  track,  too,  this  nomenclature,  just  as 
on  shipboard,  never  changes.  For  example,  on  a 
double  track  right-hand  railroad  running  due  east 
and  west  the  south  side  is  always  the  right-hand 
side  of  the  east-bound  track,  and  the  north  side 
the  right-hand  side  of  the  west-bound  track,  no 
matter  in  which  direction  an  observer  is  facing. 

On  a  single  track  railroad  this  rule  does  not  hold 
good.  Taking  a  line  running  due  east  and  west, 
for  example.  The  south  side  is  the  right-hand  side 
for  an  east-bound  train,  and  vice  versa  for  a  west- 
bound train. 

It  might  really  be  more  accurate  to  say  that  a  sig- 
nal should  be  placed  to  the  right  of  the  train  it 
governs,  but  the  American  Railway  Association  in 
its  standard  rules  has  used  the  expression  first 
given,  i.  e.,  that  a  signal  should  be  placed  to  the 
right  of  the  track  it  governs,  and  this  wording  has 
been  taken  up  by  several  state  railway  commissions 
in  their  published  rules,  so  that  it  has  become  al- 
most a  standard  expression,  and  its  meaning  is  per- 
fectly clear  to  most  railroad  men. 


IN  THEOET  AND  PRACTICE. 


31 


There  are  cases  where  some  permanent  obstruc- 
tion to  the  view  renders  it  inadvisable  to  place  the 
signal  to  the  right  of  the  track  it  governs,  and  my 
experience  has  led  me  to  believe  that  no  very  great 
harm  is  done  when  it  is  not  so  placed.  It  is  far 
more  important  to  have  a  signal  conspicuously 
placed  than  to  have  it  placed  correctly  from  a 
theoretical  standpoint,  without  reference  to  whether 
it  can  be  seen  from  an  approaching  train  or  not. 

As  a  matter  of  fact,  no  man  is  allowed  to  run  an 
engine  on  any  railroad  who  is  not  familiar  with 
the  road,  unless  he  is  accompanied  by  a  pilot  who 
is  familiar  with  it,  and  knows  what  signals  he  is 
to  look  out  for.  However,  as  a  general  thing  it  is 
much  better  to  place  signals  uniformly  wherever 
they  can  be  seen  if  so  placed  by  a  person  whose 
actions  they  are  intended  to  govern. 

In  some  cases,  as  that  of  a  three  or  four  track 
line,  it  is  impossible  to  place  a  signal  governing 
the  inside  track  between  it  and  the  outside  track. 
In  such  cases  a  so-called  bracket  pole  is  used,  or 
sometimes  a  signal  bridge.  See  Fig.  9. 

Where  the  bracket  pole  is  used  the  term  mast 


Fig.  9. 


is  applied  to  the  small  pole  above  the  bracket.  This 
is  also  frequently  called  a  doll  pole.  The  signals 
displayed  from  the  inside  mast  govern  the  inside 
track  and  those  from  the  outside  mast  govern  the 


32  EAILWAY  SIGNALING 

outside  track.  Where  a  signal  bridge  is  used  the 
signals  attached  to  masts  similar  to  those  used  on 
the  bracket  pole  are  placed  either  directly  over  the 
right-hand  rail  of  the  track  they  govern  or  over 
the  center  of  that  track.  The  latter  will  be  found 
to  be  the  better  practice,  because  in  case  of  signals 
for  one  direction  being  displayed  over  one  track 
and  for  the  opposite  direction  on  the  next  track 
to  its  right,  as  will  be  the  case  with  the  two  middle 
tracks  of  a  four-track  line,  where  the  tracks  are 
used  alternately  for  movements  in  either  direction — 
that  is,  taking  an  east  and  west  line,  if  the  north 
track  is  used  for  west  bound,  the  second  from  the 
north  for  east  bound,  the  third  from  the  north  for 
west  bound  and  the  south  track  for  east  bound, 
the  blades  of  the  signals  will  overlap  each  other 
if  the  masts  are  placed  over  the  right-hand  rail.  Fig. 
9  shows  a  four-track  line  signaled  by  both  bracket 
poles  and  a  signal  bridge,  using  the  conventional 
sign  for  the  bridge. 

Sometimes  the  signal  cannot  be  placed  to  the 
right  of  the  track  it  governs,  but  can  be  placed  one 
track  further  to  the  right,  yet  this  second  track 
may  require  no  signal.  A  bracket  pole  is  then 
frequently  used  with  a  signal  displayed  from  the 
inside  mast  and  no  signal  on  the  outside  mast,  as 
shown  at  No.  7,  Fig.  9,  where  the  signal  governs 
trains  running  on  track  C  D  and  no  signal  govern- 
ing trains  on  track  A  B  is  displayed  from  the  same 
bracket  pole. 

Another  case  is  illustrated  with  signals  8  and  9 
in  the  same  figure.  Here  there  are  three  masts  on 
the  bracket  pole,  from  the  two  outside  ones  of 
which,  only,  signals  are  displayed.  This  means  that 
the  outside  signal  governs  the  outside  track;  the 
next  track  has  no  signal,  and  the  inside  signal 
governs  the  third  track. 


IN  THEOEY  AND  PRACTICE.  33 

The  use  of  bracket  poles  with  more  than  two 
masts  should  be  avoided,  and  where  there  are  more 
than  four  tracks  parallel  to  each  other  on  any  of 
which  fixed  signals  are  to  be  displayed,  it  will  gen- 
erally be  found  that  the  use  of  signal  bridges  is 
more  satisfactory  than  the  use  of  bracket  poles. 

Where  route  signals  are  placed  on  bracket  poles 
or  bridges  some  signal  engineers  who  follow  out 
the  practice  of  signaling  low  speed  routes  with 
dwarf  signals,  in  the  case  of  single  poles,  will  allow 
the  use  of  lower  high  arms.  In  my  opinion  this  is 
not  good  practice,  and  a  dwarf  signal  on  the  ground 
had  better  be  used. 

In  the  foregoing  I  have  endeavored  to  lay  before 
the  reader  as  succinctly  as  possible  what  is  known 
as  the  language  of  fixed  signals. 

The  intelligence  conveyed  by  a  fixed  signal  such 
as  a  distant  signal  displayed  at  caution,  meaning 
proceed  prepared  to  stop,  at  the  home  signal  half  a 
mile  further  on,  or  the  lower  blade  on  a  home  route 
signal  mast  displayed  at  clear,  meaning  proceed  by 
the  inferior  route,  is  known  as  the  indication  of 
the  signal. 

The  appearance  of  the  signal  itself  is  known  as 
its  aspect. 

For  instance:  In  a  two-position  signal  system 
we  would  say  that  the  aspect  of  the  caution  indica- 
tion is  a  green  blade  with  a  forked  end  displayed  in 
the  horizontal  position,  while  the  aspect  of  the  in- 
dication for  "proceed  by  the  inferior  route"  at  a 
junction  is  a  red  blade  displayed  in  the  inclined 
position  beneath  a  red  blade  displayed  in  the  hori- 
zontal position. 

So  far  I  have  said  very  little  regarding  night 
indications,  and  only  mention  that  subject  now  to 
show  the  reader  that  I  have  not  overlooked  it.  I 
believe  it  is  better  to  become  thoroughly  familiar 


34  KAILWA7  SIGNALING 

with  the  day  indications  before  taking  up  the  sub- 
ject of  night  indications,  and  shall,  therefore,  post- 
pone what  I  have  to  say  on  that  head  to  some 
later  chapter. 

As  the  next  branch  of  our  subject  we  shall  come 
to  is  that  of  interlocking  by  which  it  is  rendered 
impossible  for  the  person  handling  the  signals  and 
switches  at  points  where  routes  are  changed  to 
display  anything  but  the  proper  signals  for  a  given 
route,  I  want  to  say  a  word  before  closing  this 
chapter  about  derailing  switches,  commonly  called 
derails. 

These  are  contrivances  placed  in  the  track  by 
which  an  engine  or  train  which  has  overrun  a  stop 
signal  will  be  thrown  from  the  track.  There  are 
many  types  of  derails  which  will  be  taken  up  in 
detail  in  the  proper  place.  They  are  generally 
shown  on  track  plans  as  at  No.  12,  Fig.  9,  and  for 
the  present  we  will  so  show  them  on  all  figures  un- 
til we  have  taken  up  the  various  types  in  detail. 

We  shall  now  take  up  the  subject  of  interlocking. 


CHAPTER  III. 

INTERLOCKING — MECHANICAL. 

The  definition  of  interlocking  given  by  the  Ameri- 
can Railway  Association  is  fan  arrangement  of 
switch,  lock  and  signal  appliances,  so  intercon- 
nected that  their  movements  must  succeed  each 
other  in  a  predetermined  orderl 

It  is  quite  possible  to  fulfill  the  requirements  of 
the  definition  by  apparatus  wherein  the  mechanisms 
by  which  the  switches,  signals,  etc.,  are  moved  are 
separated  by  considerable  distances.  Wherever 
this  is  done  these  mechanisms  must  be  operated  by 
different  persons  or  the  person  who  does  operate 
them  must  move  from  place  to  place,  entailing  a 
considerable  loss  of  time  and  needless  expenditure 
of  labor.  It  is,  therefore,  much  more  convenient 
.to  assemble  all  the  operating  machinery  in  one  place 
and  to  transmit  the  power  by  which  the  switches 
and  signals  are  to  be  moved  from  this  central  loca- 
tion. 

In  the  earlier  interlocking  arrangements  the  only 
power  used  was  manual,  and  instead  of  throwing 
the  switches  by  the  usual  revolving  switch  stands, 
it  was  found  more  convenient  to  use  levers. 

For  the  sake  of  uniformity  similar  levers  were 
used  for  the  signals  and  such  other  devices  as  it  was 
found  expedient  to  have  operated  in  connection  there- 
with. These  levers  were  and  are  placed  in  a  frame 
side  by  side.  When  this  was  done  it  was  found 
much  more  convenient  and  economical  to  interlock 

35 


36  RAILWAY  SIGNALING 

the  levers  with  each  other  than  to  interlock  tht 
switches  and  signals  out  on  the  ground. 

This  combination  of  levers  and  interlocking 
makes  the  interlocking  machine. 

Where  manual  power  is  used  to  move  the 
switches,  signals,  etc.,  the  levers  of  the  interlocking 
machine  perform  two  offices — that  of  actually  trans- 
mitting the  force  exerted  by  the  person  handling 
them  to  the  device  to  be  moved,  and  also  that  of 
locking  and  unlocking  such  other  levers  as  the  par- 
ticular combination  then  to  be  used  requires. 

Where  some  other  form  of  power  than  muscular 
strength  is  used  the  levers  in  the  machine  open 
and  close  electric  circuits  or  valves  through  which 
the  power  used  is  transmitted  to  the  operating  de- 
vices, and  also  operate  the  locking  in  the  same  way 
as  in  a  manual  machine. 

There  are  several  types  of  interlocking  machines, 
differing  from  each  other  in  their  form  of  con- 
struction, but  the  following  rules  are  general  to  all : 

(1)  The  front  of  the  machine  is  that  side  on 
which  the  person  operating  it  stands,  when  doing 
so. 

(2)  The  levers  are  numbered  from  the  left  of 
a  person  standing  facing  the  front  of  the  machine 
to  his  right,  number  one  lever  being  always  at  his 
left  hand,  and  the  highest  numbered  lever  in  that 
particular  machine  at  his  right. 

Locking  may  be  either  vertical  or  horizontal. 

One  type  which  is  most  generally  horizontal  ac- 
complishes its  purpose  in  the  folowing  manner: 

The  lever  is  attached  by  a  crank  to  a  rectangular 
bar  of  steel  in  such  a  way  that  the  first  movement 
of  the  lever,  or  of  any  part  of  it,  'slides  this  bar 
horizontally  in  a  vertical  plane  parallel  to  the  row 
of  levers  in  the  machine,  and  from  right  to  left. 
Riveted  to  the  upper  side  of  this  bar  are  steel  dogs 


IN  THEORY  AND  PEACTICE.  37 

with  wedge  shaped  ends.  At  right  angles  to  this  bar 
and  across  the  top  of  it  are  laid  other  bars  in  which 
slots  or  notches  are  cut  opposite  to  or  nearly  op- 
posite to  such  of  the  dogs  as  come  near  this  cross 
bar. 

The  first  mentioned  bars  are  called  locking  bars, 
and  those  which  lie  across  them  are  called  cross 
locks;  and  to  simplify  the  explanation  they  will 
be  so  called  hereafter. 

Both  the  locking  bars  and  the  cross  locks  are 
held  in  place  by  guides  so  that  they  are  free  to  move 
only  longitudinally. 

If  the  notch  in  a  cross  lock  is  so  shaped  that  the 
dog  on  the  locking  bar  cannot  pass  through  it 
when  the  cross  lock  is  in  its  normal  position,  but 
by  virtue  of  its  wedge  shape  can  slide  the  cross  lock 
along  longitudinally  into  a  position  in  which  the 
notch  comes  directly  opposite  the  dog  so  that  it 
(the  dog)  can  pass  through  the  cross  lock,  the  lock- 
ing bar  is  then  free  to  make  its  travel.  If,  however, 
a  dog  attached  to  another  locking  bar  is  already 
passed  through  the  cross  lock  so  that  the  cross  lock 
cannot  move  longitudinally  (the  guides  preventing 
its  movement  in  any  other  direction),  then  the  dog 
on  the  first  locking  bar  cannot  pass  through  it,  and 
the  first  bar  cannot  move,  i.  e.,  is  locked  by  the 
second  bar. 

Fig.  10  will  serve  to  illustrate  this  more  clearly. 
In  it  are  shown  a  front  view,  a  side  view  and  a 
plan  of  three  short  locking  bars,  numbered  1,  2  and 
3,  each  with  a  dog  on  it,  and  a  piece  of  cross  lock 
notched  for  each  of  these  dogs. 

The  shape  of  the  notches  in  the  cross  lock  is 
shown  by  the  dotted  lines,  and  the  shape  of  such 
part  of  the  dogs  as  is  entered  in  the  notches  of  the 
cross  lock  is  shown  also  by  dotted  lines. 

Reference  to  the  plan  will  show  that  in  the  posi- 


38 


SAILWAY  SIGNALING 


tion  given  locking  bar  2  is  free  to  move  in  the 
direction  of  its  arrow,  because  the  notch  in  the 
cross-lock  is  directly  opposite  its  dog. 

The  dog  on  No.  3  locking  bar,  it  will  be  noticed, 
passes  completely  through  the  cross-lock,  thereby 
preventing  the  movement  of  the  cross-lock  in  either 
direction  indicated  by  the  double-headed  arrow,  and 
the  guides  (which  are  omitted  from  the  drawing, 
both  from  the  cross-locks  and  the  locking  bars, 
for  the  sake  of  clearness)  prevent  its  moving  side- 
ways. 

No.  1  locking  bar  cannot  be  moved  in  the  direc- 
tion of  its  arrow,  because  the  center  line  of  its  dog 
and  the  center  line  of  the  notch  in  the  cross-lock, 


front  View, 


1 

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1       -  — 

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2 

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1          -  — 

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Plan. 

•  Side.  View. 

a*  Cross  Lock. 

..b  -Dogs 

c  =  Locking  Bars 


3       (Shown  £  Actual 5ize) 


Fig.  10. 

which  notch  is  exactly  large  enough  for  the  dog  to 
pass  through,  are  in  two  different  vertical  planes. 
No.  1  locking  bar,  therefore,  is  locked  by  No.  3. 

Now  if  No.  3  is  moved  in  the  direction  of  its 
arrow  until  its  dog  assumes  the  position  indicated 
by  the  shaded  lines,  No.  I  will  be  free  to  move  in 
the  direction  of  its  arrow,  because  No.  3's  dog  will 
have  moved  free  of  engagement  with  the  cross-lock. 
Nevertheless,  when  No.  1  does  move,  its  dog  will 
shove  the  cross-lock  down  against  the  wedge  end  of 


IN  THEORY  AND  PRACTICE.  39 

No.  3's  dog,  and  at  the  same  time  will  move  the 
center  line  of  the  notches  opposite  No.  2's  and  No. 
3's  dogs  into  vertical  planes  not  coincident  with  the 
vertical  planes  in  which  the  center  lines  of  No.  2's 
and  3's  dogs  move. 

This  movement  of  No.  1  locking  bar,  therefore, 
it  will  readily  be  seen,  locks  No.  2  bar  from  moving 
in  the  direction  of  its  arrow,  and  No.  3  bar  from 
moving  back  into  its  original  position. 

As  a  matter  of  fact  the  position  in  which  the  lock- 
ing bars  are  habitually  kept,  known  as  their  normal 
position,  is  as  far  to  the  right  as  they  are  permitted 
to  travel,  and  as  this  figure  presupposes  that  all  bars 
are  in  their  normal  position  at  the  start,  this  last 
movement  of  No.  1  locking  bar  locks  No.  2  locking 
bar  in  its  normal  position. 

The  travel  of  the  locking  bars  from  right  to  left 
is  limited  by  the  stroke  of  the  cranks  by  which 
they  are  connected  with  the  lever,  which  is  1J4  in- 
ches, and  when  they  have  traveled  as  far  to  the  left 
as  it  is  possible  for  them  to  go,  they  are  said  to  be 
in  their  reversed  position. 

For  the  sake  of  brevity  the  word  position  is 
usually  omitted  and  the  condition  existing  in  the 
last  described  position  of  the  locking  shown  in  the 
figure  would  be  explained  by  saying  that  No.  I  lock- 
ing bar  reversed  locks  No.  2  locking  bar  normal  and 
No.  3  locking  bar  reversed. 

The  foregoing  gives  a  general  outline  of  the  prin- 
ciples on  which  the  locking  of  the  improved  Saxby 
and  Farmer  interlocking  machine  is  founded.  This 
machine  is  by  far  the  most  generally  used  in  the 
United  States,  where  a  machine  with  horizontal 
locking  is  required  for  use  with  a  man-power  inter- 
locking arrangement.  The  same  principle  of  lock- 
ing, too,  is  used  on  some  of  the  machines  which 


40 


EA1LWAJ  SIGNALING 


serve  to  transmit  some  other  power  than  a  man's 
to  throw  the  switches,  signals,  etc. 
Fig.  II  shows  a  sectional  view  and  Fig.  12  a  front 


_fr-jttttt 

ii    (I A       \-^ 


IN  THEOSY  AND  PEACT1CE.  41 

view  of  an  Soever  improved  Saxby  and  Farmer 
interlocking  machine.  By  reference  to  the  side 
view  the  reader  will  see  that  the  lever  is  held  in 
its  place  at  either  end  of  its  stroke  by  a  latch 
which  is  pressed  downward  by  a  strong  coil  spring, 
so  as  to  engage  notches  shown  as  a  a1  in  the  ends 
of  two  cast  iron  guides  between  which  the  lever 
passes  in  its  stroke.  The  upper  edges  of  these 
guides  are  curved  and  form  an  arc  of  a  circle  with 


Fig.  12. 

the  pivot  of  the  lever  as  its  center.  The  lever  can 
only  be  moved  in  either  direction  by  the  operator 
pressing  in  on  the  latch  handle  with  force  enough 
to  overcome  the  resistance  of  the  spring,  or  by  an- 
other movement  which  we  will  shortly  mention. 
If  after  the  latch  is  moved  in  this  way  the  lever  is 
also  moved,  the  latch  may  again  be  released,  and 
slides  along  the  top  of  the  guide  until  the  lever 
reaches  the  end  of  its  stroke,  when  it  will  be 


42  RAILWAY  SIGNALING 

pushed  down  by  the  spring  into  the  notch  at  that 
end,  thereby  holding  the  lever  firmly  in  place.  The 
guides  which  are  usually  cast  together  in  one  piece 
are  .called  the  quadrant — a  misnomer,  by  the  way, 
as  the  curved  side  does  not  form  the  fourth  part  of 
the  circle  which  the  bottom  side  of  the  latch  would 
describe  if  the  lever  was  revolved  completely  around 
on  its  pivot. 

The  latch  has  a  projection  from  one  side  which 
engages  a  slot  in  what  is  known  as  the  rocker, 
which  is  placed  alongside  of  the  lever  in  a  plane 
parallel  to  the  plane  in  which  it,  the  lever,  moves. 
It  is  shown  as  b  in  the  figure.  This  rocker,  it  will 
be  noticed,  is  pivoted  in  the  middle,  but  is  free  to 
move  vertically  up  and  down  at  the  ends.  When 
the  latch  is  down  in  the  notch  a,  that  end  of  the 
rocker  is  pressed  down,  and  the  other  end  is 
raised  up.  In  this  position,  although  the  circle  of 
which  the  slot  in  the  rocker  is  an  arc,  is  of 
virtually  the  same  radius  as  the  circle  of  which  the 
upper  edge  of  the  quadrant  is  also  an  arc,  these 
circles  are  not  concentric,  but  when  the  latch  is 
raised  that  end  of  the  rocker  also  comes  up,  depress- 
ing its  other  end  and  bringing  it  into  a  position 
where  its  circle  is  concentric  with  the  circle  whose 
center  is  the  pivot  of  the  lever.  As  the  lever  is 
moved,  therefore,  the  projection  from  the  latch 
slides  through  the  curved  slot  of  the  rocker,  just 
as  the  bottom  face  of  the  latch  slides  along  the 
upper  side  of  the  quadrant.  This  arrangement 
plays  a  very  important  part  in  the  improved  Saxby 
and  Farmer  machine,  as  will  shortly  be  seen. 

As  a  matter  of  fact,  persons  used  to  handling 
these  machines  frequently  raise  the  latch  when  the 
levers  are  in  the  position  shown  in  the  figure  by 
pressing  down  on  the  front  of  the  rocker,  with  the 
foot,  which  raises  the  latch  and  closes  the  latch 


IN  THEORY  AND  PRACTICE.  43 

handle  in  against  the  lever  just  as  if  the  hand  was 
closed  on  it,  but  this  in  no  way  affects  the  working 
of  the  mechanism  which  we  are  explaining. 

It  should  here  be  fully  understood  that  the  opera- 
tor or  leverman,  as  he  is  generally  called,  always 
stands  on  the  same  side  of  the  machine  as  notch  a1 
in  the  quadrant — that  is,  so  that  when  the  lever  is 
in  the  same  position  as  shown  in  the  figure  it  leans 
away  from  him,  and  in  order  to  move  it  he  must 
pull  it  towards  him.  As  before  stated,  the  side  on 
which  he  stands  is  the  front  of  the  machine,  and 
the  front  of  all  parts  of  the  machine  is  towards  that 
side. 

At  the  back  end  of  the  rocker,  it  will  be  noticed, 
is  a  connection  known  as  the  universal  link,  shown 
as  c  in  the  figure.  One  end  of  this  universal  link  is 
attached  to  the  rocker  by  a  pin,  and  it  moves  up  or 
down  with  the  back  end  of  the  rocker. 

The  other  end  is  attached  to  a  short  crank 
(better  seen  in  the  front  view  of  the  machine)  and 
marked  d.  This  crank  is  rigidly  attached  to  a 
square  shaft  with  turned  journals  resting  in  bear- 
ings behind  the  levers,  and  with  its  axis  parallel  to 
the  plane  of  the  lever's  stroke. 

It  will  now  be  readily  seen  that  when  the  latch 
handle  is  closed  in  to  the  lever,  and  the  latch 
raised,  bringing  with  it  one  end  or  the  other  of  the 
rocker,  the  universal  link  is  either  raised  or  lowered 
according  to  which  end  of  its  stroke  the  lever  is  in, 
and  a  rotary  motion  is  imparted  to  the  locking 
shaft. 

The  locking  bars  already  described  lie  between 
their  guides — called  brackets — over  the  locking 
shafts.  By  a  specially  designed  crank  called  the 
driving  piece  one  or  more  of  them  is  attached  to 
each  locking  shaft.  As  the  locking  shaft  revolves 
(to  the  left,  if  the  lever  is  at  the  back  of  its  stroke, 


44  EAILWAY  SIGNALING 

and  to  the  right  if  the  lever  is  at  the  front  of  its 
stroke,  when  the  latch  is  raised),  it  slides  the  lock- 
ing bar  or  bars  to  which  it  is  attached  to  the  left  or 
right  with  it,  thereby  moving  such  dogs  as  are  riveted 
thereto  and  performing  such  locking  as  is  required  of 
it.  If,  of  course,  the  cross-locks  are  so  held  by  dogs 
attached  to  other  locking  bars  that  one  or  more  dogs 
attached  to  the  particular  locking  bar  we  are  discus- 
sing cannot  move,  the  locking  bar,  as  already  seen,  is 
also  held  fast,  in  turn  holding  the  locking  shaft, 
the  universal  link,  the  rocker,  and  lastly  the  latch. 
Until  the  latch  can  be  raised  the  lever  cannot  be 
jnoved. 

This  is  known  as  preliminary  or  latch  locking, 
and  is  one  of  the  most  ingenious  and  useful  refine- 
ments known  to  signal  engineers.  Its  use  insures 
that  a  lever  has  not  only  made  its  full  stroke,  but  is 
securely  latched  in  its  final  position  before  any  con- 
flicting lever  is  unlocked,  and  also  that  the  lever- 
man  cannot  throw  his  full  strength  against  the  lever 
when  locked.  Where  no  preliminary  locking  is 
used,  very  powerful  men  have  been  known  to  force 
levers  over  by  tearing  the  locking  loose  when  they 
have  thrown  their  full  weight  and  strength  against 
them. 

No  American  railroad  will  accept  an  interlocking 
machine  by  which  switches  or  derails  are  operated 
any  distance  away,  which  does  not  have  this  fea- 
ture, and  State  authorities  whose  duty  it  is  to  in- 
spect such  devices,  rigidly  enforce  its  use. 

The  assembly  of  locking  shafts,  locking  bars,  cross 
locks,  brackets  and  supports  for  same,  is  known 
as  the  locking  bed.  The  supports  on  either  side  of 
the  machine,  as  shown  in  the  figure,  are  the  legs; 
the  cross  piece  on  which  the  levers  are  pivoted  is 
the  bottom  rail;  the  plate  which  connects  the  legs 
together  at  the  top  is  the  top  plate. 


IN  THEOEY  AND  PRACTICE. 


45 


For  a  more  detailed  description  of  each  of  these 
various  pieces  the  reader  is  advised  to  secure  a 
copy  of  the  catalogue  of  one  of  the  large  signal 
companies. 

Machines  are  made  in  four  and  eight  lever  sec- 
tions. A  20-lever  machine,  for  instance,  would  be 
built  up  of  two  8-lever  and  one  4-lever  sections.  It 
would  have  four  legs,  two  eight-way,  and  one  four- 
way  top  plates,  two  eight-way,  and  one  four-way 
bottom  rails,  and  a  locking  bed  long  enough  and 
wide  enough  for  a  20-lever  machine. 

Vertical  locking  is  usually  of  a  different  design 
from  the  Saxby  and  Farmer  locking  first  described, 
although  one  signal  company  has  recently  put  a 


src: 


VERTICAL  LOCKING. 


Fig.  13. 

Saxby  and  Farmer  machine  on  the  market,  so  ar- 
ranged that  the  locking  may  be  placed  vertically. 

In  the  most  frequently  used  types  of  vertical 
locking,  the  movement  of  the  lever  latch  slides  a  so- 
called  tappet  vertically  up  and  down.  This  tappet 
has  V-shaped  notches  cut  in  its  edges  which  engage 
flat,  pointed  dogs  fastened  to  locking  bars  to  which 
other  dogs  may  be  fastened,  which  in  turn  engage 
the  tappets  of  other  levers,  thus  performing  the 
locking. 

Fig.    13    shows   parts   of   three   tappets,    with   the 


46 


RAILWAY  SIGNALING 


necessary  dogs  to  perform  the  same  locking  as  al- 
ready described  for  the  Saxby  and  Farmer  ma- 
chine, viz. :  No.  1  reversed  locks,  No.  2  normal;  and 
No.  3  reversed. 

Fig.  14  shows  a  sectional  side  view  and  a  front 
view  of  one  style  of  interlocking  machine  with  ver- 
tical locking.  The  rocker,  it  will  be  noticed,  is 
below  the  quadrant,  and  is  connected  to  the  tappet 


Fig.  14. 


by  a  flat  bar  called  the  connecting  link.  When 
latch  is  raised  with  the  lever  thrown  backward  as 
shown  in  the  figure,  the  front  end  of  the  rocker  is 
depressed,  and  through  this  connecting  link  slides 
the  tappet  downwards  ;  the  reverse  being  true  when 


IN  THEOET  AND  PEACTICE.  47 

the  latch  is  raised  with  the  lever  in  the  front  posi- 
tion. 

There  is  a  greater  variety  of  interlocking  ma- 
chines with  vertical  locking  than  with  horizontal 
locking,  as  the  Johnson,  the  National,  the  Standard, 
and  the  Style  A,  but  they  differ  only  in  details  of 
construction,  and  anyone  who  understands  the  in- 
terlocking of  one  of  them  will  readily  understand 
it  of  all. 

There  is  another  type  of  interlocking  machine 
known  as  the  Stevens,  the  locking  of  which  is 
similar  to  that  of  the  vertical  type  already  described, 
except  that  it  lies  in  a  horizontal  or  curved  locking 
bed.  The  tappets  are  attached  directly  to  the  lever, 
and  there  is  no  preliminary  locking  in  this  type  of 
machine.  It  should,  therefore,  not  be  used  for 
work  where  switches  and  derails  are  to  be  thrown 
at  any  distance  from  the  machine. 

There  is  some  difference  of  opinion  as  to  the 
merits  of  the  horizontal  and  vertical  locking  among 
signal  engineers,  but  I  believe  I  am  safe  in  saying 
that  the  improved  Saxby  and  Farmer  type  of  hori- 
zontal locking  is  favored  by  the  majority.  There 
are  some  situations  where  the  width  of  the  room  in 
which  the  interlocking  machine  is  to  be  placed  is 
limited  where  it  is  very  convenient  to  use  vertical 
locking. 

Interlocking  machines  by  which  the  muscular 
power  of  the  operator  is  used  to  throw  the  switches, 
signals,  etc,  are  known  amongst  Signal  Engineers 
as  mechanical  interlocking  machines.  Where  com- 
pressed air  or  electricity  is  used  to  throw  the 
switches,  signals,  etc.,  and  the  strength  of  the  oper- 
ator is  only  required  to  move  the  locking  in  the 
machine,  and  to  open  and  close  the  valves  or  con- 
tacts by  which  the  power  is  turned  on  to  the  oper- 


48 


RAILWAY  SIGNALING 


ating  device,  the  machines  are  called  power  inter- 
locking machines. 

This  nomenclature  is  probably  not  the  best,  but 
it  has  been  accepted  and  is  now  so  thoroughly  a 
part  of  the  tecnique  of  the  profession  that  I  shall 
use  these  names  hereafter  throughout  this  work. 

The  following  rule  is  general  to  all  mechanical 
interlocking  machines : 

When  normal  the  levers  are  always  in  the  posi- 
tion shown  in  the  two  foregoing  cuts ;  that  is,  lean- 
ing away  from  the  front  of  the  machine. 

In  all  interlocking  machines  one  lever  when  re- 
versed may  lock  another,  in  three  ways: 

(1)  Normal. 

(2)  Reversed. 

(3)  Normal  and  reversed. 

We  have  seen  how  the  first  two  may  be  ac- 
complished. Fig.  15  shows  the  method  of  accomp- 


) 

0  1         I 

1 

)  ( 

D\           \ 

2 

Fig.  15. 

lishing  the  third  by  either  the  Saxby  and  Farmer, 
or  the  vertical  (flat)  locking.  In  either  case  locking 
bar  or  tappet  No.  1  when  reversed  locks  locking 
bar  or  tappet  No.  2,  both  normal  and  reversed. 

There  are  two  other  points  which  should  be  thor- 
oughly grasped,  viz: 

(1)  That  when  one  lever  reversed  through  either 
a  locking  bar  or  tappet  locks  another  lever  normal 


IN  THEORY  AND  PRACTICE. 


49 


the  opposite  condition,  i.  e.,  that  the  second  lever 
when  reversed  will  always  lock  the  first  lever  nor- 
mal, is  true. 

(2)  That,  when  one  lever  reversed  locks  another 
one  reversed,  both  levers  being  normal,  the  second 
one  always  has  the  first  one  locked  normal  and 
must  be  reversed  to  unlock  it.  This  will  be  seen  at 
once  by  reference  to  Figs.  10  and  13. 

Besides  the  simple  locking  already  described, 
special  locking  is  sometimes  required.  That  is,  it 
may  be  necessary  to  have  lever  No.  1  reversed,  for 
instance,  lock  lever  No.  2  normal  when  lever  No. 
3  is  reversed,  but  not  when  lever  No.  3  is  normal. 

Before  describing  the  manner  of  accomplishing 
this  with  the  Improved  Saxby  and  Farmer  locking, 
I  wish  to  explain  that  for  the  purpose  of  clearness 
cf  illustration  in  the  Saxby  and  Farmer  locking 
shown  in  Fig.  10,  I  have  shown  the  locking  bars 
spaced  some  little  distance  apart.  In  reality  these 
bars  are  put  into  the  locking  bed  in  pairs,  side  by 
side,  with  a  space  of  ^  in.  between  each  pair.  See 
Fig.  1 6,  which  shows  eight  locking  bars  in  section, 


Locking  bars    Bracket 


Fig.  16. 

with  side  view  of  a  cross  lock  above  them  as  they 
would  appear  in  actual  practice.  I  may  also  state 
here  that  although  the  locking  bars  are  numbered 
from  the  front  to  the  back  of  the  locking  bed  in 
consecutive  order,  as  will  be  explained  more  fully 
when  we  get  to  the  designing  of  locking  for  specific 
cases,  the  numbers  of  the  locking  bars  have  no 


50 


RAILWAY  SIGNALING 


Fig.  17. 


reference  to  the  number  of 
levers  by  which  they  are 
driven.  Number  one  lever 
may  drive  a  locking  bar  of 
any  number  or  even  two  or 
more  bars,  and  hereafter  I 
shall  refer  to  the  lever  num- 
bers only  and  omit  refer- 
ence to  the  numbers  of  the 
locking  bars. 

Fig.  17  is  a  plan  view  of 
the  eight  locking  bars  in 
Fig.  16  with  the  caps  of  the 
brackets  removed  for  clear- 
ness of  illustration. 

On  each  locking  bar  the 
black  dot  (used  for  clear- 
ness), denotes  its  driving 
piece,  or  driver,  as  it  is  com- 
monly called,  the  number  in- 
dicating the  lever  to  the 
locking  shaft  of  which  the 
driver  is  connected.  A  small 
circle,  it  may  as  well  be 
noted  here,  is  the  conven- 
tional manner  of  showing 
the  driver,  used  on  the  plan 
views  of  locking  beds  drawn 
up  and  put  into  the  hands 
of  the  mechanics  who  build 
interlocking  machines,  or 
who  make  alterations  in  the 
locking  in  the  field  after  ma- 
chines have  once  been  in- 
stalled. These  plans  are 
known  as  dog  sheets,  and 
will  be  more  fully  described 
in  their  proper  place. 


IN  THEORY  AND  PRACTICE.  51 

In  addition  to  the  regular  dogs,  it  will  be  noticed 
that  a  long  crooked  dog  is  attached  to  the  bar 
driven  by  lever  No.  3,  its  end,  however  resting  on 
the  bar  driven  by  lever  No.  6.  It  should  also  be 
noted  that  the  cross  lock  opposite  the  point  of  this 
crooked  dog  is  divided  completely  in  two,  so  that 
the  two  portions  of  it  can  move  independently  of 
each  other. 

This  crooked  dog  is  called  by  the  manufacturers 
a  tappet,  or  swing"  dog.  By  signal  men  it  is  often 
called  a  special  dog,  and  sometimes  a  "when"  dog. 
As  tappet  might  be  confused  by  a  beginner  with  the 
tappet  of  the  flat  locking,  and  as  other  special  dogs 
may  be  mentioned,  I  shall  call  these  tappets  here- 
after in  this  description  "when  dogs,"  or  "whens," 
a  name  which  is  peculiarly  significant,  as  will  soon 
be  seen. 

This  "when"  is  not  riveted  to  the  locking  bar, 
but  is  held  loosely  by  a  turned  pin  forming  part 
of  a  trunnion  which  is  riveted  to  the  bar.  This  ar- 
rangement allows  the  "when"  to  swing  in  the  same 
direction  as  the  cross  lock  will  be  moved  by  the  dog 
on  the  locking  bar  driven  by  lever  No.  I.  With 
lever  No.  3  normal  (all  levers  are  assumed  to  be 
normal  in  the  figure),  lever  No.  1  can  be  reversed 
and  its  dog  will  slide  the  portion  of  the  cross  lock 
which  it  engages  in  the  direction  of  the  when  dog,  so 
as  to  close  up  the  gap  between  it  and  the  other 
portion  of  the  cross  lock,  but  this  latter  portion  will 
not  be  moved. 

If,  however,  lever  No.  3  is  first  reversed,  the 
"when  dog"  will  slide  into  the  gap  between  the  two 
portions  of  the  cross  lock,  filling  this  gap  up.  Now 
if  lever  No.  1  is  reversed  it  will  push  the  lower 
portion  of  the  cross  lock  in  the  direction  of  the 
arrow  as  before,  but  as  the  gap-  between  the  two 
portions  of  the  cross  lock  is  now  filled  in  by  the 


52  RAILWAY  SIGNALING 

"when,"  which,  being,  pivoted  on  its  trunnion 
vSwings  away  from  the  pressure  of  the  lower  por- 
tion of  the  cross  lock,  transmitting  the  movement 
of  the  lower  portion  to  the  upper  portion,  the  dog 
on  the  locking  bar  driven  by  lever  No.  1  will  lock 
the  dog  on  the  locking  bar  driven  by  No.  2,  nor- 
mal, just  as  if  the  cross  lock  was  one  continuous 
piece.  The  condition  already  alluded  to  when  we 
first  commenced  the  consideration  of  special  lock- 
ing is,  therefore,  fulfilled.  That  is,  that  lever  No.  1 
reversed,  locks  lever  No.  2,  normal,  when  lever  No. 
3  is  reversed,  but  not  when  lever  No.  3  is  normal. 
The  significance  of  the  term  "when  dog"  will  now 
be  seen. 

There  is  another  point  which  I  want  to  call  to 
the  readers'  attention  before  going  on  to  describe 
the  method  of  accomplishing  special  locking  where 
tappet  bars  are  used.  Where  a  dog  drives  a  cross 
lock  in  such  a  way  that  all  the  locking  is  accom- 
plished on  one  side  or  the  other  of  this  dog,  it  is  not 
necessary  to  notch  the  cross  lock.  It  may  be 
divided  at  the  locking  bar  to  which  the  driving  dog 
is  attached,  and  that  portion  only  which  is  on  the 
side  of  the  dog  where  the  locking  is  to  be  accom- 
plished will  be  moved  by  it.  The  remainder  of  the 
cross  lock  may  be  driven  by  a  dog  on  some  other 
bar.  This  renders  it  possible  to  economize  in  the 
use  of  cross  locks.  As  a  rule  there  is  one  locking 
bracket  with  cross  locks  in  it  for  each  two  levers 
in  the  machine,  although  the  locking  beds  are  so 
arranged  that  intermediate  brackets  may  be  put  in, 
thus  making  a  bracket  for  each  lever.  The  neces- 
sity for  this  does  not  often  arise,  however. 

Fig.  1 8  illustrates  the  various  forms  of  dogs  used 
with  improved  Saxby  and  Farmer  locking.  When 
we  come  to  the  discussion  of  dog  sheets,  the  rea- 
sons for  the  different  shapes  will  become  apparent. 


IN  THEORY  AND  PRACTICE. 


53 


S*>  o.bl 


>r 


xo  o  o  i    0 

41 


/O  o  6  I    (S| 
/^p  e    l    O 

C|T  t^g 


.  T-I       n» 


r; 


U^v    II  II 


Fig.  18. 


d     0 


•t4     M'- 


In  machines  with  vertical  locking  beds,  where 
tappets  are  used,  the  special  locking  is  accomplished 
on  the  general  principle  of  having  a  piece  attached 


54  RAILWAY  SIGNALING 

to  the  tappet  of  the  controlling  lever,  so  arranged 
that  it  can  move  sideways.  Two  dogs  which  do  not 
move  in  the  same  vertical  plane  as  the  tappets,  but 
in  a  vertical  plane  parallel  thereto  and  immediately 
in  front  of,  or  behind  the  tappets,  according  as  the 
locking  bed  is  on  the  front  or  back  side  of  the  ma- 
chine, are  placed  on  either  side  of  this  movable 
piece.  If  the  controlling  lever  acts  in  its  normal 
position,  then  this  movable  piece  is  between  these 
dogs,  so  that  a  movement  of  the  dog  on  one  side  in 
the  direction  of  the  other  dog  will  be  transmitted 
to  the  second  dog  through  the  movable  piece.  This 


1 

1 

*—  

1    (I)    1 

p 

2                      3 

r—  1        rS 

rri             1  /\  I 

S3 

(D     < 

D    >--' 

r-  ,'  '.  :                        :::•:•              '•!>    (D    ]i 

JI0I!               1 

d 

4- 

j^ 

Fig.  19. 

second  dog  either  itself  locks  the  tappet  of  the  lever 
to  be  locked,  or  through  a  locking  bar  moves  an- 
other dog,  which  does  so.  If  the  controlling  lever 
is  reversed,  the  lever  which  drives  the  dog  on  one 
side  of  the  tappet,  will  only  drive  it  into  the  vacant 
space  left  by  the  movable  piece  which  has  been 
removed  by  the  reversing  of  the  controlling  lever. 
The  opposite  of  course  is  true,  if  the  controlling 
lever  acts  when  reversed. 

The  arrangement  of  the  details  of  this  controlling 
piece  vary  somewhat  in  different  makes  of  ma- 
chines, but  the  general  principle  is  the  same. 

Fig.   19  shows  portions  of  three  tappet  bars,  with 


IN  THEOKY  AND  PEACT1CE.  55 

the  necessary  dogs  to  do  the  same  locking  as  is  de- 
scribed for  the  Saxby  and  Farmer  machine,  viz. : 
Lever  No.  1  reversed,  locks  lever  No.  2  normal, 
when  lever  No.  3  is  reversed.  In  this  type  of  lock- 
ing, which  is  in  common  use,  a  swing  dog  fastened 
to  the  tappet  of  the  controlling  lever  serves  to  trans- 
mit the  movement  of  another  dog  moving  in  the 
same  plane  as  the  swing  dog  to  a  third,  also  in  the 
same  plane  as  the  swing  dog,  which  in  turn  either 
drives  another  dog  in  the  same  plane  as  the  tap- 
pets, or  itself  locks  a  tappet  by  having  its  other  end 
bent  so  as  to  move  in  its  plane,  or  engages  a  dog 
rigidly  fastened  to  the  tappet  so  as  to  act  in  the 
same  way  that  a  notch  in  its  edge  would  act. 

In  the  figure,  driving  dog  d,  which  is  moved  to 
the  left,  when  lever  No.  1  is  reversed,  transmits  its 
motion  to  dog  b,  which  slides  along  the  face  of  No.  3's 
tappet.  If  No.  3  is  reversed,  dog  b  strikes  the  project- 
ing side  of  swing  dog  a  and  moves  it  towards  the 
left.  The  projecting  end  of  a  on  the  other  side  in  turn 
moves  c  to  the  left.  The  end  of  c  farthest  from  a 
engages  the  dog  e  rigidly  fastened  to  tappet  No.  2, 
thereby  locking  lever  of  that  number  normal. 

If  lever  No.  3  is  normal,  as  is  the  case  in  the  fig- 
ure, dog  b  passes  into  the  recess  in  the  side  of  a  and 
does  not  move  a  at  all. 

The  special  locking  in  other  types  of  machines  is 
so  similar  to  what  has  been  described  that  I  shall  not 
take  space  to  go  into  it  more  fully.  If  the  reader  will 
examine  any  Johnson  or  National  machine,  he  will 
be  able  in  a  moment,  from  the  above  description, 
to  understand  the  special  locking  of  these  machines. 


CHAPTER  IV. 

INTERLOCKING-POWER. 

The  interlocking  of  the  levers  in  power  interlocking 
machines  is  accomplished  as  described  for  mechanical 
machines,  except  that  the  feature  of  latch  locking,  as 
applied  to  mechanical  machines,  is  sometimes,  in  fact 
more  generally,  omitted,  and  its  place  supplied  by  what 
is  known  as  the  indication. 

Before  I  go  into  the  subject  of  indications,  I  shall 
state  a  few  elementary  principles  in  the  application  of 
electricity  to  the  performance  of  mechanical  work. 

I  shall  state  these  simply  as  facts,  and  if  the  reader 
wishes  to  verify  them,  or  to  inform  himself  as  to  the 
reasons  for  their  existence,  he  should  procure  an  ele- 
mentary treatise  on  electricity  and  magnetism,  such 
as  is  given  in  the  ordinary  works  on  Natural  Phil- 
osophy used  in  high  schools. 

(1)  If  two  plates  of  different  substances  which 
form  an  electric  couple,  are  submerged  in  a  solution 
of  acid,  without  touching  each  other  after  they  are 
submerged,  and  are  then  connected  together  outside 
of  the  acid  by  an  iron  or  a  copper  wire,  an  electric 
current  will  flow  through  this  wire. 

(2)  When  designed  especially  for  the  purpose  of 
generating  electricity  the  electric  couple,  the  acid 
(called  the  electrolyte)  and  the  vessel  or  jar  in  which 
they  are  held,  taken  together,  is  called  a  cell. 

(3)  A  collection  of  one  or  more  cells  coupled  to- 
gether, is  called  a  battery. 

(4)  The  electric  current  flows  through  the  elec- 

56 


IN  THEORY  AND  PRACTICE.  57 

trolyte  from  one  plate  of  the  electric  couple  to  the 
other,  through  that  plate,  along  the  connecting 
wire  and  back  to  the  first  plate.  The  connections 
of  the  wire  to  the  plates  are  called  the  poles  of  the 
battery. 

(5)  If  the  wire  is  broken  at  any  time  the  current 
ceases  to  flow.      An  arrangement  can  be  made  by 
which  the  wire  may  be  temporarily  broken  or  tem- 
porarily connected  so  that  the  flow  of  the  current 
may  be  shut  off  or  continued  at  will.     One  of  the 
most  familiar  instances  of  this  is  an  electric  door 
bell.      We  push  on  the  button,  thereby  connecting 
the  two  ends  of  a  wire  which  passes  through  the 
bell  and  connects  the  two  poles  of  the  battery,  and 
the  bell  rings  because  we  have  completed  the  cir- 
cuit, as  it  is  called,  and  the  current  flows  through 
the  operating  mechanism  of  the  bell.      We  let  go 
of  the  button,  it  is  pushed  back  by  a  spring  and 
breaks   the  wire    (opens   the   circuit),   the   current 
ceases  to  flow  and  the  bell  stops  ringing. 

(6)  A  magnet  is  a  piece  of  stone  or  metal  which 
has  the  power  of  attracting  towards  it  iron,  and  to 
a  minor  degree  some  other  metals. 

(7)  A  natural  magnet  is  usually  a  stone  which 
has  this  power.     An  artificial  magnet  is  a  piece  of 
iron  or  steel  which  has  been  given  this  power  by 
some  artificial  means. 

(8)  Some   substances,   like  rubber  or  silk,  will 
not  carry  an  electric  current  in  appreciable  quan- 
tities.    These  are  called  insulating  substances.    An 
iron  or  copper  wire  covered  with  rubber  or  silk  is 
said  to  be  insulated. 

(9)  If  an  insulated  wire  through  which  an  elec- 
tric current  is  passing  is  wound  around  a  piece  of 
steel  or  iron  (see  Fig.  20),  the  steel  or  iron  becomes 
a  magnet.     In  the  case  of  the  steel,  after  it  has  once 
been  converted  into  a  magnet  in  this  way  and  the 


58  RAILWAY  SIGNALING 

electric  current  is  cut  off,  it  will  remain  a  magnet, 
but  in  the  case  of  pure  iron,  it  ceases  to  be  a  mag- 
net almost  instantly  after  the  flow  of  the  current 
stops. 

(10)  Within  certain  limits,  the  more  turns  of 
wire  made  around  the  steel  or  iron,  the  stronger 
the  magnet  will  become,  for  the  same  amount  of 
current.  By  winding  a  great  many  feet  of  wire 
around  a  round  soft  iron  bar,  a  few  inches  long, 
called  the  core,  and  leaving  the  two  ends  of  the 
wire  exposed  so  that  they  can  be  connected  by  other 
wires  to  the  poles  of  an  electric  battery,  we  have 
what  is  known  as  an  electro  -  magnet.  A  piece 


Fig.  20. 

of  iron  is  placed  near  one  end  of  the  core  and  is 
so  held  by  guides  that  it  cannot  get  so  far  away 
from  the  end  of  the  core  that  the  attraction  of  the 
core  when  it  is  magnetized  is  insufficient  to  lift  this 
piece  of  iron.  Every  time,  therefore,  that  an  elec- 
tric current  is  sent  through  this  coil  of  wire  (called 
the  magnet  coil)  the  core  becomes  a  magnet  and 
lifts  up  the  other  piece  of  iron,  which  is  called 
the  armature,  holding  it  up  as  long  as  the  core 
is  magnetized.  When  the  electric  current  is  cut 
off,  the  core  (being  soft  iron)  ceases  to  be  a  magnet, 
and  if  the  armature  is  at  the  bottom  side  of  the 


IN  THEORY  AND  PRACTICE.  59 

core,  it  will  fall  away  therefrom  by  gravity,  as  far 
as  its  guides  will  allow  it.  In  this  way  an  electric 
current  which  cannot  be  seen  or  heard  can  be  made 
to  perform  mechanical  work. 

The  electro-magnet  appears  everywhere  in  signal 
engineering,  and  its  principle  should  be  thoroughly 
understood. 

The  power  machines  in  most  general  use  today 
are  the  Union  Switch  and  Signal  Company's  elec- 
tro-pneumatic, the  Union  Switch  and  Signal  Com- 
pany's all  electric,  and  the  General  Railway  Signal 
Company's  all  electric.  Other  good  machines  are 
to  be  had,  but  so  far  as  the  interlocking  of  the 
levers  is  concerned,  it  will  be  enough  to  call  the 
reader's  attention  to  a  few  minor  details  in  which  the 
interlocking  of  those  machines  just  mentioned  dif- 
fers from  that  of  mechanical  machines. 

In  the  two  former,  the  locking  is  of  the  Im- 
proved Saxby  and  Farmer  type.  The  so-called 
levers  are  in  reality  cranks,  and  are  attached  directly 
to  the  locking  shafts.  The  driver,  instead  of  being 
a  specially  designed  crank,  as  is  the  case  in  the 
mechanical  machine,  is  a  small  rack  and  pinion, 
the  pinion  being  attached  to  the  locking  shaft,  and 
the  rack  being  formed  by  cutting  teeth  for  a 
short  distance  in  the  bottom  of  the  locking  bar. 

The  arrangement  of  dogs  and  cross  locks  is  much 
the  same  in  the  power  as  in  the  mechanical  ma- 
chine. 

Certain  levers  drive  the  bars  toward  the  right 
only,  and  other  levers  are  normal  in  their  mid 
stroke,  and  drive  their  locking  bars  both  to  the 
right  and  left.  This  to  some  extent  modifies  the 
shape  of  the  dogs,  and  the  manner  in  which  they 
are  fastened  to  the  locking  bars,  but  the  reasons 
for  these  modifications  are  so  apparent  to  anyone 
who  understands  the  Improved  Saxby  and  Farmer 


60  RAILWAY  SIGNALING 

interlocking  as  applied  to  mechanical  machines, 
that  a  further  discussion  of  this  side  of  the  subject 
would  be  unprofitable  here. 

The  locking  in  power  machines,  as  it  cannot  be 
subjected  to  very  rough  handling,  is  made  one-half 
the  size  of  that  in  mechanical  machines. 

The  levers  of  a  power  interlocking  machine  re- 
quire the  exercise  of  very  little  strength  on  the 
part  of  the  leverman,  as  they  are  not  connected 
directly  by  mechanical  means  to  the  switches,  sig- 
nals, etc.,  which  they  operate,  and  the  leverman 
can  not  tell  by  the  "feel"  of  the  levers,  as  is  the  case 
with  the  mechanical  machine,  whether  or  not  the 
switch  or  signal  has  responded  to  the  movement 
of  the  lever.  To  supply  this  information,  the  in- 
dication already  referred  to  has  been  introduced. 
That  particular  feature  (the  information  it  affords 
to  the  leverman)  belongs  more  especially  to  the 
operating  mechanism,  which  will  be  described  later 
on,  and  at  present  we  shall  only  describe  its  appli- 
cation, as  a  substitute  for  latch  locking.  For 
present  purposes  all  that  need  be  said  of  it,  there- 
fore, is  that  the  movement  of  a  switch,  signal  or 
other  operating  device,  closes  an  electric  circuit 
which  passes  through  the  coils  of  an  electro-magnet 
placed  in  the  frame  of  the  interlocking  machine, 
the  armature  of  which  is  attached  to  a  small  arm 
which  engages  the  lever  in  such  a  way  that  only  a 
small  part  of  the  stroke  can  be  made  until  the 
operating  device  has  done  its  full  work,  after  which 
the  'electro-magnet  is  energized  and  raises  this 
small  arm  from  engagement  with  the  lever,  so  that 
the  stroke  of  the  lever  can  be  completed,  thereby 
unlocking  any  other  lever  or  levers  which  it  is  desired 
to  unlock. 

Fig.  21  gives  a  sectional  side  view  and  part-sec- 
tions of  a  lever,  locking  shaft,  and  indication  elec- 


IN  THEORY  AND  PRACTICE. 


61 


tro-magnet  for  a  Union  Switch  and  Signal  Co.'s 
electro-pneumatic,  or  all  electric,  machine. 

There  is  a  difference  between  the  arrangement 
for  a  lever  which  operates  a  switch  and  the  arrange- 
ment for  a  lever  which  operates  a  signal.  The  lever 
illustrated  is  a  switch  lever,  and  it  will  serve  to  fully 
explain  the  application  of  the  indication,  as  a  sub- 
stitute for  latch  locking. 

It  will  be  noticed  that  near  the  back  end  of  the 


PART  SECTION  THROUGH  SWITCH  LE.VEJ2 


Lower 


SECTION  AA 


SECTION  BB 


Fig.  21. 


locking  shaft  a  segment  shown  as  a  in  the  figure 
is  secured.  This  segment  being  on  the  lower  side 
of  the  locking  shaft  swings  in  the  opposite  direction 
to  the  movement  of  the  lever. 

Two  small  enlargements  or  teeth  are  a  part  of  the 
segment,  and  a  piece  of  steel  with  two  jaws  at  one 
end,  in  general  shape  not  unlike  a  common  monkey 
wrench  with  its  jaws  open,  is  placed  so  that  one 
of  the  jaws  is  above  and  one  below  the  side  of  the 
segment  on  which  the  teeth  are.  The  distance  be- 
tween the  jaws  is  so  laid  out  that  there  is  just  space 


62  EAILWAY  SIGNALING 

enough  for  one  tooth  and  the  segment  to  pass  be- 
tween them.  The  other  end  of  the  piece  of  steel  is 
attached  to  the  armature  of  the  indication  magnet. 

When  the  magnet  is  de-energized  and  the  arma- 
ture down,  the  lower  side  of  the  upper  jaw  rests  on 
the  segment,  and  there  is  space  enough  for  the  lower 
tooth,  which,  it  will  be  noticed,  travels  in  advance 
of  the  upper  tooth,  to  pass  over  the  upper  side  of 
the  lower  jaw.  The  upper  jaw  will  engage  the 
upper  tooth,  and  stop  the  lever  when  only  part 
of  the  stroke  has  been  completed.  The  lever  is, 
however,  allowed  to  make  enough  movement  to 
close  the  path  for  the  electric  current  by  which  the 
switch  is  operated  before  the  upper  tooth  engages 
the  jaw.  When  the  switch  has  made  its  full  travel, 
the  path  for  the  electric  circuit  through  the  indica- 
tion magnet  is  closed,  current  flows  through  it,  the 
magnet  is  energized,  the  armature  is  attracted  to 
the  core,  and  raises  the  piece  of  steel  so  that  the 
upper  jaw  is  lifted  from,  and  the  lower  jaw  presses 
against  the  segment.  The  upper  tooth  can  then 
pass  under  the  upper  jaw,  and  the  lever  can  com- 
plete its  stroke.  Before  completing  it,  however,  it 
breaks  the  path  of  current  through  the  indication 
magnet,  whose  armature  then  drops  down  and 
leaves  the  jaws  in  the  same  position  as  they  were 
in  when  we  started  with  this  description,  the  teeth 
in  the  segment  being  on  the  other  side  however. 
As  the  back  of  the  teeth  is  in  the  shape  of  a  wedge, 
when  the  lever  is  returned  to  normal  the  segment 
will  pass  between  the  jaws  without  hindrance,  so 
another  segment  with  the  teeth  turned  the  other 
way  and  another  indication  magnet  are  provided  to 
take  care  of  the  movement  of  the  lever  in  the  oppo- 
site direction  to  that  just  described. 

Before  the  upper  tooth  encounters  the  upper  jaw, 
the  lever  has  made  enough  stroke  to  lock  all  other 


IN  THEOBY  AND  PRACTICE.  63 

levers  which  it  is  intended  to  lock,  but  not  enough 
to  unlock  the  levers  it  will  finally  unlock,  so  that 
the  indication  acts  exactly  as  the  latch  locking  of 
the  mechanical  machine. 

In  the  General  Railway  Signal  Co.'s  all  electric 
machine  (sometimes  known  as  the  Taylor  machine, 
from  the  fact  that  it  was  at  one  time  manufactured 
by  a  company  of  that  name),  the  locking  is  of  the 
vertical  type,  and  the  indication  operates  as  follows : 
The  levers  are  really  plungers  which  slide  hori- 
zontally backwards  and  forwards  in  the  machine 
frame  a  distance  of  4  ins.  In  their  farthest  back 
position  they  are  normal,  and  when  out  as  far 
towards  the  leverman  as  they  will  go  they  are  re- 
versed. For  something  more  than  half  their  length, 
measured  from  the  back,  they  are  a  flat  bar  of  steel 
J/2  in.  x  2  ins.  The  front  end  runs  down  to  a  square 
bar,  l/2]  in.  x  j^  in.,  and  terminates  in  a  handle  set 
vertically  to  the  axis  of  the  lever,  to  give  the  lever- 
man an  easy  hold. 

In  the  front  end  of  the  flat  part  of  the  lever  a  bent 
slot  is  cut.  In  this  slot,  which  in  all  is  the  length 
of  the  lever's  stroke,  a  small  roller  travels.  A  jaw 
at  the  upper  end  of  the  tappet  is  pinned  through 
this  roller.  When  the  lever  is  normal  this  roller  is 
as  near  the  lower  edge  of  the  lever  as  the  slot  will 
allow  it  to  go,  and  consequently  the  tappet  is  as  far 
down  in  the  locking  bed.  As  the  lever  is  reversed 
the  roller  is  raised,  bringing  the  tappet  up  with  it, 
and  accomplishing  the  necessary  locking. 

It  should  be  noted  that  the  tappet  in  this»type  of 
locking  moves  upward  from  normal,  while  in  the 
type  of  vertical  locking  already  described,  it  moves 
downward.  This  has  no  effect  on  the  movement  of 
the  dogs. 

For  a  small  part  of  the  stroke  the  tappet  is  raised. 
Then  as  the  slot  becomes  horizontal  it  remains 


64  EAILWAY  SIGNALING 

stationary,  and  finally  near  the  end  of  the  lever's 
stroke,  is  raised  again,  completing  the  locking. 

Alongside  the  lever  is  another  bar  or  plate  rigidly 
attached  to  the  machine  frame,  and  pivoted  to  whose 
side  are  three  dogs,  so  as  to  be  immediately  below 
the  bottom  of  the  lever.  Each  of  these  dogs  is  held 
in  position  by  a  flat  spring.  Three  long  notches  are 
cut  in  the  lower  side  of  the  lever.  The  first  of  these 
dogs,  a,  engages  one  of  the  notches;  the  second,  b, 
engages  the  first  dog.  The  indication  magnet  is 
placed  below  the  lever.  When  energized  its  arma- 
ture raises  a  rod  which  engages  the  dog  b  already 
referred  to. 

When  the  leverman  first  starts  to  reverse  his 
lever,  its  bottom  edge  slides  along  the  top  of  the 
first  dog  a  until  the  end  of  the  first  notch  is  reached. 
The  bottom  edge  of  the  lever  then  bears  down  on 
the  front  end  of  this  first  dog  a,  and  raises  its  back 
end,  which  is  then  free  to  move  upward  as  the  third 
notch  is  over  it.  This  releases  the  second  dog  b, 
the  upper  end  of  which  is  thrown  forward  by  its 
spring,  so  as  to  come  in  under  the  back  end  of  the 
first  dog  a  and  hold  that  end  up.  The  raised  back 
end  of  the  first  dog  a  next  encounters  the  back  of 
the  third  notch  in  the  lever,  and  the  lever's  further 
movement  is  stopped  until,  the  indication  magnet 
being  energised,  the  rod  already  mentioned  presses  up 
on  the  lower  arm  of  the  second  dog  b,  shoving  it  back 
into  its  normal  position  and  releasing  the  back  end 
of  the  first  dog  a,  which  is  then  depressed  by  its  spring, 
raising  its  front  end,  and  the  lever  can  be  pulled  out  to 
its  full  stroke. 

Fig.  22  will  serve  to  illustrate  this  if  the  reader  will 
carefully  go  over  the  above  description  with  the  figure 
before  him. 

In  setting  the  lever  normal  after  it  has  been  re- 
versed, the  indication  acts  in  practically  the  same 


IN  THEORY  AND  PBACTICE. 


65 


manner.  Dog  c  which  has  been  pulled  into  position 
shown  in  B  by  the  engagement  of  the  lug  e  with 
the  side  of  the  notch  h  is  set  back  into  the  position 
shown  in  A  by  the  first  inch  or  two  movement  of 
the  lever.  The  dog  c,  as  it  turns,  forces  the  dog  b 


B 


Fig.  22. 


into  the  position  shown  in  B  at  exactly  the  right 
instant. 

Further  on  we  will  discuss  the  subject  of  inter- 
locking more  fully  in  connection  with  the  drawing 
up  of  locking  and  dog  sheets  for  specific  cases.  The 
foregoing  description  will  serve  to  give  the  reader  a 
general  idea  of  the  mechanical  methods  followed  to 
accomplish  it  in  the  machines.  We  will,  therefore 
leave  the  subject  for  the  present  and  take  up  lock- 
ing and  operating  devices,  and  the  manner  in  which 
the  leverman  controls  them  through  the  interlock- 
ing machine. 


CHAPTER  V. 

LEADOUTS  AND  GROUND  CONNECTIONS. 

In  the  United  States  it  is  the  universal  practice 
with  mechanical  interlocking  plants  to  transmit  the 
force  exerted  on  the  levers  by  the  leverman  to  the 
mechanisms  by  which  the  switches,  signals,  etc.,  are 
moved  by  lines  of  pipe  or  by  wires. 

Where  pipe  is  used  it  is  1  in.  inside  diameter,  and 
about  1%  ins.  outside  diameter.  Where  wire  is 
used,  it  is  galvanized  steel,  generally  No.  8,  8^, 
or  9.  The  movements  of  switches  locks,  movable 
point  frogs,  and  in  short  everything  except  signals, 
are  operated  through  pipe  connections.  It  is  also 
the  more  general  practice  to  operate  home  signals 
by  pipe  connections.  Distant  signals,  except  as  will 
be  noted  later,  are  operated  by  wires,  and  dwarf  sig- 
nals are  most  frequently  wire  connected,  although 
quite  a  few  signal  engineers  prefer  to  operate  them 
by  pipe  lines. 

Starting  with  the  interlocking  machines:  these 
may  be  placed  either  in  the  upper  story  or  ground 
floor  of  a  building,  though  more  generally  they  are 
placed  in  the  upper  story.  We  will  discuss  ma- 
chines so  placed  first.  Fig.  23  shows  the  side  view 
of  a  lever  for  a  machine  so  placed,  to  which  a  pipe 
line  is  to  be  attached.  It  should  be  noted  that  the 
lever  is  bent  around  at  almost  a  right  angle.  In 
the  end  farthest  away  from  the  handle  a  hole  is 
drilled,  and  what  is  known  as  a  solid  jaw  (see  Fig. 
23),  is  attached  to  the  lever  by  a  turned  pin,  of  %  in. 


IN  THEORY  AND  PRACTICE. 


67 


diameter,  which  is  kept  in  place  by  a  spring  cotter 
passed  through  a  hole  in  its  end. 

The  jaw  is  continued  into  a  piece  of  1  5-16  in. 
round  iron,  the  other  end  of  which  is  tanged;  that 
is,  it  is  reduced  to  one  inch  in  diameter,  with  an 
even  shoulder  around  it,  as  is  shown  in  the  figure. 
Just  beyond  this  shoulder  where  the  iron  is  still 


(J>  0      O 


Fig.  23. 

1  5-16  in.  in  diameter  a  thread  is  cut  for  about  1  in., 
better  a  little  more,  and  a  pipe  coupling  is  screwed 
on.  A  hole  ^4  in-  m  diameter  is  punched  or  drilled 
through  the  small  portion  as  shown.  The  end  of  a 
1  in.  pipe,  which  is  threaded  to  fit  the  coupling,  is 
passed  over  the  1  in.  portion  of  the  tang  and 


68  RAILWAY  SIGNALING 

screwed  into  the  coupling  until  its  end  butts  nearly 
or  quite  up  against  the  shoulder,  after  which  a  hole 
is  punched  through  it,  corresponding  to  the  hole  in 
the  tang  and  a  %  in.  soft  iron  rivet  put  through 
and  riveted  down. 

In  case  one  length  of  pipe  is  not  sufficient  to 
reach  from  the  machine  to  the  lower  floor  of  the 
building  another  length  of  pipe  may  be  joined  to 
the  first  length,  as  follows :  Each  length  of  pipe  is 
threaded  on  both  ends.  On  one  end  a  coupling  is 
screwed ;  on  the  other  end  there  is  no  coupling.  In 
the  end  on  which  the  coupling  is  screwed,  a  so- 
called  plug  is  inserted.  This  plug,  see  Fig.  24,  is  a 
piece  of  1  in.  round  iron  cut  to  the  required  length, 
and  inserted  for  one-half  its  length  in  the  end  of  the 


Fig.  24. 

pipe,  where  it  is  held  in  place  by  one  or  two  %  in- 
rivets.  ^  The  other  half  of  its  length  is  left  project- 
ing beyond  the  end  of  the  pipe,  and  the  second 
length  of  pipe  can  be  attached  to  the  first  exactly  as 
described  for  the  tang  end  of  the  jaw. 

As  a  rule  one  length  of  pipe  is  more  than  suffi- 
cient to  reach  from  the  machine  to  the  ground  floor 
of  the  building,  but  this  method  of  jointing  the  pipes 
is  used  wherever  two  pipes  are  joined,  so  the  de- 
scription is  as  appropriate  here  as  it  would  have  been 
further  on. 

When  a  pipe  line  of  sufficient  length  to  reach 
from  the  lever  nearly  to  the  ground  floor  has  been 
secured,  another  jaw  is  fastened  to  the  down  end 


IN  THEOBY  AND  PRACTICE. 


69 


of  the  pipe  just  as  the  first  jaw  was  fastened  to  the 
upper  end. 

When  the  ground  floor  is  reached  it  is  necessary 
to  change  the  direction  of  the  pipe  line  from  vertical 
to  horizontal. 

There  are  three  accepted  methods  of  doing  this, 
as  follows: 

(1)  By  using  vertical  cranks. 

(2)  By  using  rocking  shafts. 

(3)  By  using  vertical  deflecting  bars. 

Fig.  25  shows,  a,  a  vertical  crank  and  b  a  vertical 
deflecting  bar. 

In  the  case  of  the  vertical  crank  and  the  deflect- 
ing bar,  it  is  easy  to  see  from  the  figure  how  the 


Fig.  25.  ^ 

jaw  at  the  lower  end  of  the  pipe  connecting  with 
the  lever  is  pinned  to  that,  just  as  the  jaw  at  the 
upper  end  was  pinned  to  the  lever.  With  the  rock- 
ing shaft  this  it  not  quite  so  apparent,  and  a  short 
description  will  here  be  given.  The  rocking  shaft 
is  a  bar  of  hexagonal,  round,  or  preferably,  square  iron 
or  steel,  which  as  per  Fig.  26,  is  supported  hori- 
zontally in  a  vertical  plane  parallel  to  the  vertical 
plane  in  which  the  pipe  leading  down  from  the  lever 
moves.  To  its  end  a  crank  is  attached  which  swings 
in  a  plane  perpendicular  to  the  axis  of  the  rocking 


70 


EAILWAY  SIGNALING 


shaft.  The  jaw  in  the  lower  end  of  the  pipe,  which 
in  the  case  of  the  rocking  shaft  must  be  so  fitted 
that  its  opening  is  at  right  angles  to  the  opening 
in  the  upper  jaw,  is  pinned  to  this  crank.  When  the 
lever  is  moved  backwards  and  forwards,  a  rotary 
motion  is  imparted  to  the  rocking  shaft.  Another 
crank  is  attached  to  the  rocking  shaft  at  right  angles 
to  the  axis  of  the  first  crank. 

As  a  general  thing  the  buildings  in  which  inter- 
locking machines  are  situated,  and  especially  those 
where  the  machine  is  placed  in  an  upper  story,  are 
built  so  that  the  row  of  levers  in  the  machine  is  paral- 


Flg.  26. 

lei  to  a  track  in  front  of  the  building,  and  the  position 
of  at  least  some  of  the  switches  or  signals  to  be  op- 
erated requires  that  the  lines  of  pipe  by  which  they 
are  operated  should  turn  away  to  the  right  or  left 
hand  as  soon  as  they  get  outside  of  the  building.  The 
rocking  shaft  is  peculiarly  well  adapted  for  this,  as 
another  jaw  can  be  pinned  to  the  second  crank  and  a 
pipe  line  attached  to  it  whose  direction  is  at  right 
angles  to  the  axis  of  the  rocking  shaft  and  parallel  to 
the  row  of  levers. 

Where  the  vertical  crank  or  the  vertical  deflecting 
bar  is  used,  this  turn  is  not  so  easily  made,  but  re- 
quires the  introduction  of  an  additional  crank  or  de- 
flecting bar  laid  horizontally  and  connected,  by  a  piece 
of  pipe  with  a  jaw  fastened  to  each  end,  to  the  arm 


IN  THEORY  AND  PRACTICE.  71 

of  the  vertical  crank  not  connected  to  the  lever,  or  to 
the  lower  end  of  the  vertical  deflecting  bar.  Some- 
times for  the  sake  of  economizing  space,  several  hori- 
zontal cranks  are  placed  in  one  frame.  This  is  called 
a  box  crank. 

Fig.  27  shows  a  single,  generally  called  "one  way" 
horizontal  crank,  a  horizontal  deflecting  bar,  and  a 
six  way  box  crank. 


Fig.  27. 

The  arrangement  of  vertical  cranks,  rocking  shafts, 
vertical  deflecting  bars,  the  connections  between  them 
and  the  levers,  horizontal  cranks,  box  cranks  or  hori- 
zontal deflecting  bars  and  connections  between  them 
and  the  vertical  cranks  or  deflecting  bars,  by  which 
the  direction  of  the  power  of  the  lever  is  changed  im- 
mediately in  front  of  the  building,  taken  together,  is 
known  as  the  lead-out. 

Where  a  building  is  built  especially  for  the  shelter 
of  the  interlocking  machine  and  the  attending  lever- 


72 


RAILWAY  SIGNALING 


men,  and  in  which  the  machine  is  placed  in  an  upper 
story,  it  is  known  as  the  tower,  and  wherever  here- 
after in  this  work  I  use  the  name  lead-out  or  tower, 
the  foregoing  should  be  taken  as  an  explanation  of 
these  terms. 

Fig.  2&  shows  a  side  view  of  three  levers  connected 
respectively  to  a  rocking  shaft,  a  vertical  crank,  and 
a  vertical  deflecting  bar. 

It  may  be  said  in  passing  that  for  neatness  of  ap- 
pearance it  is  always  better,  when  possible,  to  build 
the  entire  lead-out  of  one  device  or  the  other. 

Where  signals  are  operated  by  wires  for  reasons 


Fig.  28. 

which  will  be  explained  more  fully  later,  two  wires  are 
now  always  used.  The  lever  then  has  an  addition  ex- 
tended from  its  front,  as  shown  in  Fig.  29,  to  which 
one  of  the  wires  is  attached,  known  as  the  tail  lever, 
the  other  wire  being  attached  to  the  back  end  of  the 
lever  the  same  as  a  pipe  line. 

When  the  lever  is  reversed,  one  wire  is  pulled  on, 
while  the  other  one  is  slacked  away,  and  when  the 
lever  is  set  at  normal  again  this  process  is  reversed. 


IN  THEORY  AND  PRACTICE. 


73 


The  method  of  fastening  the  wires  to  the  levers  is 
to  provide  a  clevis,  known  as  a  shackle,  or  an  adjust- 
able connector  which  slips  over  the  tail  lever  and  back 
end  of  the  lever  proper  and  is  held  in  place  with  a  set 
screw.  Through  this  shackle  or  connector  a  grooved 
metal  eye,  known  as  a  wire  eye,  is  passed.  The  wire  is 
then  passed  around  the  groove  in  the  wire  eye  and 
wrapped  several  times  around  itself. 

On  the  ground  floor  of  the  tower  two  iron  pulleys, 

known  as  vertical  chain 
wheels,  are  placed. 
Pieces  of  one  -  quarter 
inch  straight  link  chain, 
about  four  feet  long  are 
run  through  these  pul- 
leys. A  split  link  is 
slipped  through  the  end 
link  of  the  chain,  a  wire 
eye  passed  through  that, 
and  the  wire  attached  to 
the  wire  eye  in  the  man- 
ner already  explained. 

The  introduction  of  this 
chain  is  necessary  in 
order  to  have  a  flexible 
belt  around  the  pulley 
large  enough  not  to  pass 
between  the  pulley  and 
its  frame,  and  besides 
this,  if  the  wire  itself 
was  run  around  the  pul- 
ley,  the  constant  bending 
and  then  straightening 
out  it  would  be  subjected 
to  would  soon  break  it. 
If  it  is  desired  to  change  the  direction  of  the  wire 
line  in  front  of  the  tower,  a  horizontal  chain  wheel 


Fig.  29. 


74  EAILWAY  SIGNALING 

with  two  sheaves  is  used.  If  there  are  several  wire 
lines  to  be  changed,  several  of  these  wheels  are  put 
together  in  one  frame,  and  are  then  known  as  a  box 
chain  wheel.  The  chain  wheels,  both  vertical  and  hori- 
zontal, placed  inside  of  or  immediately  outside  of  the 
tower,  are  also  included  in  the  term  lead-out. 

Where  machines  are,  like  those  we  have  just  been 
considering,  arranged  to  be  placed  in  upper  stories  of 
the  tower  and  to  connect  through  vertical  pipes  or 
wires  with  vertical  cranks,  vertical  deflecting  bars,  or 
with  rocking  shafts,  or  vertical  chain  wheels,  they  are 
said  to  be  vertical  lead-out  machines. 

Where  they  are  arranged  to  be  placed  on  the  ground 
floor  of  the  building,  they  are  said  to  be  horizontal 
lead-out  machines.  Either  horizontal  or  vertical  lock- 
ing beds  are  used  with  vertical  lead-out  machines. 
Horizontal  lead-out  machines  almost  invariably  have 
horizontal  locking  beds. 

In  horizontal  lead-out  machines,  the  levers  are  not 
as  a  rule  fulcrumed  at  their  lowest  point,  but  at  a  point 
part  way  up  the  leg  of  the  machine.  An  exception  to 
this  rule  is  one  type  of  the  Stevens  machine.  The  lev- 
ers have  no  bent  ends  and  are  connected  by  jaws  and 
pipe  directly  to  horizontal  deflecting  bars  or  cranks. 
Rocking,  shafts  are  not  used  with  these  machines. 
Where  a  lever  operates  a  wire  line,  one  of  two  ar- 
rangements is  usually  adopted: 

(1)  The  lever,  by  jaws  and  pipe,  is  connected  with 
one  arm  of  a  three-arm  horizontal  crank  to  the  other 
two  arms  of  which  the  wires  are  connected  by  shackles 
or  adjustable  connectors.    See  Fig.  32. 

(2)  The  lever,  by  a  jaw,  is  connected  to  a  short 
pipe  line  into  which  a  so-called  pipe  lug  is  introduced 
by  its  tang  ends.    A  piece  of  ^-in.  straight  link  chain 
is  attached  to  this  lug  and  is  then  rove  back  around 
the  pulley  of  a  vertical  chain  wheel.     The  end  of  the 
pipe  not  attached  to  the  lever  is  supplied  with  a  shackle 
to  which  the  wire  is  in  turn  attached. 


IN  THEORY  AND  PRACTICE.  75 

A  movement  of  the  lever  in  either  case  therefore 
pulls  on  one  wire  and  slacks  away  on  the  other.  Fig. 
30  will  serve  to  make  this  description  clear  at  a 
glance. 

After  leaving  the  tower  the  pipe  lines  are  guided 
and  supported  by  pipe  carriers. 

A  pipe  carrier  consists  of  two  stands  or  sides  made 
of  malleable  or  cast  iron  between  which  is  supported 
a  bottom  roller  and  a  top  roller,  spaced  far  enough 
apart  to  allow  the  pipe  to  move  freely  between  them. 
Where  the  pipe  crosses  a  track  these  pipe  carriers  are 
supported  by  a  wrought  iron  or  malleable  iron  bridge, 
the  ends  of  which  are  fastened  to  two  adjacent  ties, 
and  are  then  called  transverse  pipe  carriers.  Where 
the  pipe  lines  run  out  in  the  open  the  pipe  carriers  are 
fastened  to  what  are  known  as  pipe  carrier  tops.  These 
tops  in  turn  are  fastened  to  foundations  which  are 
buried  in  the  ground. 

The  pipe  carrier  sides  or  stands  are  so  arranged  that 


Fig.  30. 

in  case  several  pipe  lines  run  parallel  to  each  other, 
one  side  can  be  added  with  an  additional  top  and  bot- 
tom roller  and  space  provided  in  that  way  for  another 
pipe.  With  all  the  parts  assembled  pipe  carriers  are 
generally  designated  by  the  number  of  pipes  they 
carry  parallel  to  each  other,  as  three  way,  four  way, 
five  way,  etc.,  meaning  that  they  are  arranged  to  carry 
three,  four,  or  five  parallel  pipes.  A  three  way  pipe 
carrier  would  have  four  sides  or  stands,  three  bottom 
and  three  top  rollers,  and  in  all  cases  a  pipe  carrier  of 
any  given  way  will  have  one  more  side  than  the  num- 


76 


RAILWAY  SIGNALING 


her  of  way,  and  as  many  of  each  of  the  top  and  bottom 
rollers  as  there  are  ways. 

Generally  speaking  the  tops  to  which  the  pipe  car- 
riers, other  than  the  transverse,  are  attached  are 
blocks  of  oak  wood,  3  ins.  x  8  ins.  in  section,  and  cut 
to  the  required  length,  and  the  pipe  carrier  sides  are 
fastened  to  them  by  lag  screws.  There  are  one  or  two 
metal  tops  now  on  the  market  which  are  used  to  some 


FIfl.  31. 

extent,  and  the  use  of  which  will  no  doubt  become 
more  general  as  the  price  of  lumber  advances. 

Formerly  it  was  the  general  practice  to  make  these 
tops  part  of  a  rectangular  wooden  frame  much  like  the 
four  sides  of  a  box,  which  was  buried  in  the  ground 
with  one  side  exposed  and  acted  as  a  foundation  and 
top  as  well;  but  of  recent  years  the  foundations  have 
been  made  of  concrete  or  cast  iron,  and  the  tops  bolted 


IN  THEORY  AND  PEACT1CE. 


77 


to  them.  Probably  90  per  cent  of  modern  installations 
use  concrete  foundations. 

Fig.  31  shows  a  one  way  transverse  pipe  carrier, 
a  two  way  ordinary  pipe  carrier  and  a  top  which  is 
fastened  to  two  concrete  foundations  of  a  form  very 
frequently  used. 

Some  designs  of  transverse  pipe  carriers  have  no  top 
roller  and  there  is  another  style  of  pipe  carrier,  known 
as  a  special  ivrought  pipe  carrier,  which  has  no  top 
roller  and  is  intended  to  be  screwed  down  to  the  end 
of  the  ties  where  it  is  necessary  to  run  pipes  very  close 
to  the  rail.  Their  use  at  interlocking  plants  is  gen- 
erally confined  to  locations  around  switches,  or  to 
steady  the  up  and  down  pipes  leading  from  the  levers 
to  the  floor  of  the  tower  with  a  vertical  lead-out  ma- 
chine. They  will  be  shown  in  some  of  the  figures 
which  will  appear  later. 

As  all  pipe  lines  end  with  jaws  which  are  pinned  to 
the  levers,  cranks,  etc.,  with  %  in.  round  pins,  the  unit 


I 


Fig.  32. 

of  strength  for  any  pipe  line  may  be  considered  as  that 
of  a  %  in.  round  pin  in  double  shear.  The  pipe  line 
may  be  considered  as  a  hollow  column  supported  at 
each  end;  and  calculation  and  experience  have  shown 
that  the  pipe  carriers  should  not  be  placed  more  than 
7  ft.  apart  in  order  that  the  pipe  will  not  bend  side- 
ways before  the  pins  give  way.  Some  signal  engi- 
neers place  them  7  ft.  apart  on  straight  lines,  and  6  ft. 
apart  on  curves. 

Wires  after  they  leave  the  tower  are  generally  sup- 


78  RAILWAY  SIGNALING 

ported  by  small  metal  pulleys  known  as  wire  carriers, 
a  popular  form  of  which  is  shown  in  Fig.  32. 

As  long  as  there  are  pipe  lines  going  in  the  same  di- 
rection as  the  wires,  these  wire  carriers  are  fastened 
by  screws  to  every  fourth  pipe  carrier  top,  so  as  to 
space  them  21  ft  apart.  As  the  wire  is  never  in  com- 
pression there  is  no  mathematical  reason  for  this  dis- 
tance, and  where  pipe  carriers  are  spaced  6  ft.  apart 
the  wire  carriers  may  be  placed  on  every  fourth  top 
as  before,  making  them  18  ft.  apart  instead  of  21  ft. 

Where  the  wires  go  out  to  distant  signals  they  gen- 
erally extend  far  beyond  the  pipe  lines,  and  then  it  is 
customary  to  drive  oak  stakes  3  ins.  x  4  ins.,  and  4  ft. 
long,  pointed  at  one  end,  every  21  ft.,  and  to  screw 
the  pipe  carriers  to  the  tops  of  these  stakes. 

The  row  of  stakes  is  generally  set  parallel  to  the 
track,  and  if  the  track  happens  to  be  curved,  the  tops 
of  the  stakes  are  sawed  off  on  a  bevel  and  the  wire 
carriers  are  set  at  an  angle  to  the  vertical,  so  that 
when  the  wire  is  in  tension  the  force  exerted  by  it 
against  the  rim  of  the  pulley  wheel  will  bear  directly 
against  the  pin  on  which  the  pulley  wheel  turns.  This 
is  done  in  order  to  get  the  mechanical  advantage  of 
the  pulley,  and  not  have  the  wire  scraping  against  the 
side  of  the  frame  of  the  wire  carrier  as  it  would  do 
otherwise. 

A  wire  carrier  which  is  hinged  in  such  a  way  that 
it  may  be  set  at  any  desired  angle  and  then  clamped 
in  that  position  is  used  to  some  extent.  Its  use  ob- 
viates the  necessity  of  bevelling  the  top  of  the  stakes. 

Attempts  have  been  made  from  time  to  time  to  in- 
troduce metal  wire  stakes,  but  it  can  hardly  be  said 
that  their  use  so  far  has  become  standard  practice, 
most  signal  engineers  still  retaining  the  oak  stakes. 

To  return  to  the  pipe  line.  Where  a  moderate  curve 
such  as  following  the  curvature  of  a  track  up  to  8,  or 
on  page  79. 


IN  THEOEY  AND  PRACTICE. 


79 


even  10  degrees,  is  to  be  made  in  it,  the  pipe  may  be 
sprung*  a  little  to  follow  this  curve. 

The  middle  ordinate  for  a  7  ft.  chord  of  a  circle 
with  the  radius  of  a  10  degree  curve  is  only  about  %  in. 

Where,  however,  a  sudden  turn  is  to  be  made,  such 
as  might  be  necessary  at  the  angle  of  a  crossing  of  two 
railroad  tracks,  horizontal  deflecting  bars,  radial  arms, 
or  cranks  are  introduced. 


Fig.  33. 

The  deflecting  bars  used  in  such  cases  are  similar  to 
those  already  described,  except  that  they  do  not  gen- 
erally make  a  complete  90  degree  turn  in  the  pipe  line. 
In  fact  where  the  turn  is  greater  than  45  degrees  the 
use  of  cranks  will  be  found  more  satisfactory. 

Radial  arms  are  not  much  used  except  where  a  pipe 
line  crosses  a  track  between  the  ties,  and  is  then  turned 
so  as  to  cross  another  track  which  does  not  run  quite 
parallel  though  nearly  so  to  the  first  track.  By  far 
the  most  common  device  for  effecting  turns  is  the  hori- 


80  RAILWAY  SIGNALING 

zontal  crank.  By  bending  its  arms  a  turn  of  almost 
any  angle  may  be  made  in  the  pipe  line. 

Fig.  33  shows  a  three  way  horizontal  deflecting  bar, 
a  one  way  radial  arm  (these  radial  arms  are  made  up 
to  three  way)  and  a  right  angle,  an  obtuse  angle,  and 
an  acute  angle  crank. 

As  before  stated  the  levers  in  the  interlocking  ma- 
chine are  spaced  5  ins.  apart,  center  to  center,  and  of 
course  the  vertical  cranks,  vertical  deflecting  bars  or 
rocking  shafts  in  the  lead-out  are  so  spaced  also.  The 
pipe  carriers  are  so  arranged  that  parallel  pipe  lines 
after  leaving  the  lead-out  are  spaced  2^4  ins.  apart, 
center  to  center.  The  box  cranks  or  any  other  hori- 
zontal cranks  used  in  the  lead-out,  therefore,  must  be 
so  arranged  that  the  pin  holes  in  one  arm  must  meas- 
ure 5  ins.,  center  to  center,  while  in  the  other  arm  they 
must  measure  2^4  ms->  center  to  center.  With  the 
rocking  shaft  this  change  of  spacing  is  easily  effected, 
as  the  crank  on  the  body  of  the  shaft  may  be  driven 
along  it  to  any  desired  position. 


CHAPTER  VI. 

COMPENSATION OFFSETS — FOUNDATIONS. 

Having  now  seen  how  we  bring  the  pipe  lines  from 
the  levers  in  the  tower  out  onto  the  ground,  and  how 
we  can  then  turn  them  in  any  direction  we  please,  we 
will  say  a  few  words  on  compensation,  which  is  by  far 
the  most  important  item  to  be  taken  into  consideration 
in  the  ground  work  of  a  mechanical  interlocking  plant. 

It  is  a  well-known  fact  that  iron  and  steel  expand 
when  heated,  and  contract  when  chilled;  and  the  pipe 
in  an  interlocking  plant  being  subjected  to  the  effect 
of  the  hot  sun  of  summer  and  the  bitter  cold  of  win- 
ter, lengthens  and  shortens  considerably.  Roughly 
speaking,  iron  and  steel  expand  about  1  in.  in  100  ft. 
for  each  100  degrees  Fahrenheit  rise  in  temperature, 
and  contract  correspondingly.  As  there  are  many  sec- 
tions of  the  United  States  where  it  is  not  uncommon 
to  have  temperatures  of  100  degrees  in  the  sun  in 
summer,  and  of  25  to  30  degrees  below  zero  in  the 
winter,  and  as  pipe  lines  are  frequently  over  1,000  ft. 
long,  it  can  easily  be  seen  that  this  expansion  and  con- 
traction is  a  very  serious  matter. 

In  order  to  neutralize  its  effect,  compensators  are  let 
into  each  pipe  line.  The  established  rule  is  to  have  a 
compensator  in  each  pipe  line  over  50  ft.  in  length 
and  up  to  800  ft.  in  length.  For  pipe  lines  over  800 
and  less  than  1,200  ft.  in  length  a  compensator  with 
longer  arms  is  used.  For  pipe  lines  over  1,200  ft.  two 
or  more  compensators  are  provided. 

81 


82  -RAILWAY  SIGNALING 

The  simplest  form  of  compensator  is  a  straight  bar 
pivoted  in  the  middle  in  an  ordinary  crank  stand.  Sup- 
pose a  perfectly  straight  pipe  line  attached  at  one 
end  to  a  lever,  and  at  the  other  end  to  some  device 
like  a  semaphore.  Also  suppose  that  the  lever  is 
latched  and  cannot  be  moved,  and  the  semaphore  blade 
is  as  far  as  its  attachments  will  allow  it  to  go  in  the 
direction  that  a  push  on  the  pipe  line  would  send  it. 
Then  suppose  the  pipe  line  to  be  heated  so  that  it  will 
expand  3  ins.  It  must  either  break  something,  or  itself 
bend,  carrying  the  pipe  carriers  and  foundation  with  it. 

Suppose,  however,  that  we  cut  the  pipe  line  in  two 


Fig.  34. 

in  the  middle,  attach  a  jaw  to  each  of  the  ends  (we 
are  supposing  that  pipe  equal  in  length  to  the  two 
jaws  will  be  cut  out)  and  pin  these  jaws  to  the  ends  of 
the  compensator  arm.  Now  when  the  half  of  the  pipe 
between  the  compensator  and  the  lever  expands  its 
1%  ins.,  the  lever  end  being  held  fast,  the  compensator 
end  will  move,  taking  the  end  of  the  compensator  arm 
to  which  it  is  attached  with  it.  At  the  same  time  the 
other  half  of  the  pipe  line  which  is  held  fast  at  the 
signal,  is  expanding  just  as  much  towards  its  com- 
pensator arm,  and  we  have  two  parallel  forces  acting 
in  opposite  directions  on  either  end  of  an  equal  arm 
lever  which  simply  tends  to  turn  the  lever  around  on  its 
fulcrum. 

In  actual  practice  this  type  of  compensator  is  awk- 
ward to  use  because  it  makes  a  jog  in  the  pipe  line 
wherever  introduced,  and  the  so-called  lazy  jack  com- 


IN  THEORY  AND  PRACTICE.  83 

pensator  which  keeps  both  parts  of  the  pipe  line  in 
the  same  vertical  plane  has  been  designed. 

Fig.  34  shows  one  of  these  devices.  It  consists  of 
an  acute  angle  crank,  and  an  obtuse  angle  crank,  both 
pinned  to  one  frame  and  a  link  connecting  them.  A 
glance  at  the  figure  will  show  the  reader  how  a  pull 
on  one  pipe  in  the  direction  of  the  arrow  will  make  a 
corresponding  push  on  the  other  pipe  in  the  opposite 
direction,  and  yet  both  pipes  remain  in  the  same  verti- 
cal plane,  allowing,  of  course,  for  the  slight  sidewise 
movement  which  the  end  of  the  crank  arms  give  them 
as  they  swing,  which  is  so  slight  it  may  be  disregarded. 

As  each  foot  of  the  pipe  line  expands  or  contracts 
as  much  as  and  no  more  than  any  other  foot,  it  is 
easy  to  see  why  when  only  one  compensator  is  pro- 
vided, it  should  be  placed  in  the  middle  of  the  line  to 
be  compensated.  If  this  was  not  done,  as  the  arms  of 
the  compensators  work  together,  they  would  travel  as 
much  as  the  longer  pipe  line  expanded  or  contracted, 
and  as  the  shorter  pipe  line  would  not  expand  or  con- 
tract as  much  it  would  either  be  subjected  to  a 
severe  tension  or  compression,  which  might  break  it 
or  bend  it,  or  give  a  wrong  movement  to  the  switch 
or  signal. 

The  amount  of  contraction  or  expansion  which  can 
be  taken  up  by  one  lazy  jack  compensator  is  limited 
and  the  use  of  compensators  with  different  sized 
cranks  is  often  inconvenient.  In  actual  practice  I  have 
found  it  worked  out  very  well  to  let  a  compensator 
into  each  line  50  ft.  to  650  ft.,  to  have  two  compen- 
sators in  every  line  650  to  1,300  ft.,  three,  compensators 
for  1,300  to  1,950  ft.,  and  so  on. 

Where  two  compensators  are  used  in  a  line,  the 
distance  to  be  compensated  should  be  divided  into  four 
equal  parts,  and  the  compensators  should  be  placed  at 
the  first  and  third  points  of  division  so  that  there  is 
just  twice  as  much  pipe  line  between  the  two  compen- 


84 


RAILWAY  SIGNALING 


sators  as  there  is  between  either  compensator  and  the 
fixed  end  nearest  it.  Each  compensator  will  then  take 
up  one-half  of  the  expansion  or  contraction  of  the  line 
between  it  and  the  other  compensator  which  will  be 
equal  to  the  expansion  of  the  line  between  it  and  the 
nearest  fixed  end. 

With  three  compensators  the  line  should  be  divided 
into  six  equal  parts  and  the  compensators  set  at  the 
first,  third  and  fifth  points  of  division. 

It  should  be  thoroughly  understood  that  a  compen- 
sator always  reverses  the  direction  of  application  of  the 
power.  That  is,  if  the  pipe  on  one  side  is  being  shoved 


Fig.  35. 


I A 


toward  the  compensator  this  will  be  changed  into  a  pull 
on  the  pipe  on  the  other  side. 

So  far  we  have  considered  only  compensation  in 
straight  lines.  If  any  cranks  are  introduced  into  a 
line  to  change  its  direction,  they  may  or  may  not  have 
an  effect  upon  the  placing  of  the  compensators  in  that 
line. 

Fig.  35  shows  a  pipe  line  connected  to  a  vertical 
crank,  the  other  arm  of  which  is  connected  to  a  pipe 
line  in  which  several  horizontal  cranks  are  introduced. 
The  paper  is  supposed  to  represent  the  plane  of  the 
ground,  and  for  convenience  of  illustration  the  vertical 
crank  is  shown  as  if  it  was  laid  down  on  its  side.  If 
the  lever  is  reversed  it  will  be  readily  seen  that  a  pull  is 
exerted  on  the  pipe  line  up  to  the  compensator.  There 
it  is  reversed  and  changed  into  a  shove.  We  will  as- 


IN  THEORY  AND  PRACTICE.  85 

sume,  however,  that  it  is  necessary  to  have  a  pull  at 
the  switch,  and  the  last  crank,  it  will  be  seen,  is  set 
around  in  such  a  way  that  a  shove  on  one  arm  will  pro- 
duce a  pull  on  the  other.  This  crank,  therefore,  acts 
exactly  as  a  compensator  does  in  addition  to  its  regular 
duty  of  changing  the  direction  of  the  pipe  line.  In 
laying  out  the  compensation,  therefore,  a  distance 
equal  to  that  from  the  crank  to  the  switch  should  be 
laid  out  on  the  other  side  of  the  crank,  and  the  length 
of  pipe  which  the  regular  compensator  is  to  take  care 
of  should  be  figured  from  this  point,  shown  as  A  in 
the  Fig.,  and  the  compensator  placed  half  way  between 
A  and  the  lever. 

Besides  the  solid  jaws  already  described,  what  are 
known  as  screw  jaws  are  also  used  to  some  extent. 
One  of  these  is  shown  in  Fig.  36.  The  principal  dif- 


Fig.  36. 

ference  between  it  and  the  solid  jaw  is  that  the  jaw 
part  is  threaded  and  can  be  screwed  backward  and 
forward  on  the  shank  so  as  to  lengthen  or  shorten  the 
pipe  line.  These  are  useful  in  taking  up  wear,  slight 
variations  in  length  of  pipe  line  caused  by  the  settling 
of  foundations,  etc.  Some  signal  engineers  use  them 
to  connect  the  pipe  lines  to  the  arms  of  the  compen- 
sators, instead  of  solid  jaws,  but  more  generally  their 
use  is  confined  to  connections  to  switches,  locks  and 
signals.  Turn  buckles  called  point  adjusting  screws 
are  also  frequently  let  into  the  pipe  line  for  adjustment 
purposes.  It  is  good  practice  to  have  at  least  one  in 
every  pipe  line.  To  have  one  somewhere  in  the  line 
on  each  side  of  each  compensator,  unless  one  end  or 
the  other  terminates  in  a  screw  jaw,  in  which  case  the 
point  adjusting  screw  may  be  omitted,  will  be  found 
very  convenient. 


86  RAILWAY  SIGNALING 

Where  there  are  several  pipe  lines  running  parallel, 
and  a  compensator  is  to  be  let  into  one  of  them,  it 
must  be  placed  in  a  different  horizontal  plane  (on  a 
different  level)  usually  below  the  pipe  lines  so  as  not 
to  interfere  with  them. 

The  jaws  by  which  the  pipes  and  compensators  are 
connected  are  then  bent  as  shown  in  Fig.  37  so  as  to 
make  an  offset,  and  the  compensator  arms  move  freely 
below  the  other  pipes. 

It  is  frequently  necessary  to  offset  jaws  connecting 
pipe  lines  with  cranks,  deflecting  bars  and  radial  arms 
in  the  same  way.  These  offsets  should  not  be  greater 
than  2%  ins.  in  one  place.  If  more  is  needed  the  crank 
arms  or  whatever  the  pipe  is  to  be  connected  to,  may 
be  given  an  additional  offset  in  the  other  direction,  not 
to  exceed  2  ins.,  so  as  to  make  4%  ins.  change  in  all, 
and  if  it  is  a  crank  the  other  arm  can  be  offset  another 
2  ins.,  making  6%  ins,,  and  the  other  jaw  may  be  bent 


Fig.  37. 

like  the  first,  giving  a  total  of  11  ins.  Where  a  greater 
offset  than  2%  ins.  is  required  in  the  pipe  line  at  some 
point  where  no  compensator,  crank,  radial  arm,  or  de- 
flecting bar  is  placed,  a  bar  of  1%  ins.  round  iron, 
tanged  on  each  end  should  be  let  into  the  pipe,  and  as 
many  2^  ins.  offsets  placed  not  less  than  1  ft.  apart, 
made  in  that  as  is  necessary  to  total  the  required  off- 
set. This  sort  of  work,  although  permissible  and 
strong  enough,  never  looks  well,  however,  and  should 
be  avoided  wherever  possible. 

Where  a  certain  amount  of  offset  is  required  at  a 
crank  it  always  looks  better  to  divide  it  equally  be- 
tween the  two  jaws  and  the  two  crank  arms.  The  pipe 
itself  should  never  be  bent. 


IN  THEORY  AND  PRACTICE. 


87 


Where  wire  connections  are  used  the  wire  of  course 
expands  and  contracts,  just  as  the  pipe  does.  As  it  is 
never  drawn  very  taut  when  first  put  in  there  is  little 
chance  of  its  contracting  enough  to  break.  Its  sup- 
ports being  set  21  ft.  apart,  it  is  bound  to  sag  down 
more  or  less  between  them,  and  to  a  certain  extent  acts 
as  its  own  compensator  in  that  way. 

As  before  stated,  wire  adjusting  screws  are  univer- 
sally provided  in  the  base  of  the  tower,  so  that  in  case 
of  any  very  sudden  changes  in  temperature  the  lever- 
man  in  a  minute  or  two  can  readjust  the  wires. 
n 


Fig.  38. 

Nevertheless  wire  compensators  have  been  invented 
and  are  to  be  had  from  the  dealers,  although  their  use 
is  very  limited  at  the  present  time.  Fig.  38  shows  two 
separate  designs,  the  principles  of  which  are  so  self- 
evident  that  I  shall  not  describe  them  in  detail. 

Cranks,  compensators,  deflecting  bars,  radial  arms 
and  chain  wheels  are  usually  supported  on  concrete 
foundations  buried  in  the  ground.  These  foundations 
are  made  very  much  larger  than  those  already  men- 


88  RAILWAY  SIGNALING 

tioned,  which  support  the  pipe  carriers,  because 
they  are  actually  subjected  to  the  strain  on  the 
pipe  or  wire  line  when  the  leverman  moves  his  lever. 
Nothing  is  more  vexatious  than  to  have  one  or 
more  of  these  foundations  move  after  an  interlock- 
ing plant  is  completed,  and  if  there  is  any  doubt  as 
to  the  solidity  of  the  ground  it  is  best  to  stand  on 
the  safe  side  and  be  sure  to  make  them  large 
enough. 

I  have  found  the  following  sizes  to  be  a  good 
average,  but  as  before  stated  if  the  ground  is 
marshy  or  very  light  they  had  better  be  made  larger. 

For  cranks :  26  in.  wide,  26  in.  long  and  3  ft.  deep. 

For  compensators:  26  in.  wide,  52  in.  long  and  3 
ft.  deep. 

For  deflecting  bars,  24  in.  x  24  in.  x  3  ft. 

For  radial  arms  and  chain  wheels:  24  in.  x  24  in. 
x3  ft. 

On  account  of  their  size  it  is  not  convenient  to 
ship  them  around;  and  the  quite  general  practice  is 
to  dig  a  hole  of  the  proper  dimensions,  suspend  the 
crank,  compensator  or  whatever  device  is  to  be  set,  in 
its  proper  position  over  the  hole,  and  fill  in  with  con- 
crete. In  sandy,  loose  soils,  it  is  frequently  neces- 
sary to  make  forms  to  reach  to  the  bottom  of  the 
hole,  but  in  stiff  soils  a  form  around  the  top  to  give 
that  part  of  the  foundation  which  shows  above 
ground  a  neat  appearance  is  all  that  is  necessary. 
It  is  very  important  that  the  bottom  of  the  hole  be 
kept  level,  so  that  the  concrete  will  set  with  a  flat 
base.  If  the  sides  are  allowed  to  cave  into  the  hole, 
the  concrete  foundation  or  block  is  apt  to  be  made 
with  a  rounded  bottom,  and  is  then  more  likely  to 
rock  when  a  strain  is  put  on  the  pipe  line  than  it 
would  be  if  it  stood  on  a  flat  base. 

The  cranks,  compensators,  etc.,  are  secured  to 
the  concrete  block  in  one  of  three  ways : 


IN  THEOEY  AND  PRACTICE. 


89 


(1)  By  being  bolted  to  blocks  of  oak  through 
which  and  extending  out  from  their  lower  side,  are 
4  24 -in.  hook  bolts  long  enough  to  reach  nearly  to 
the  bottom  of  the  concrete,  which  is  rilled  in  around 
these  hook  bolts. 

(2)  The  same  as  above,  except    that    the    oak 
block  is  omitted  and  the  upper  ends  of    the  hook 
bolts  are  passed  through  the  base  of  the  device  to 
be  fastened  down. 

(3)  By  using  cast  iron  legs  or  piers,  the  tops 
of  which  are  grooved  so  as  to  take  the  head  of  a 
short  %  in.  bolt  slipped  in  from  the  end  of  the 
groove.      The    thread   end   of   the   bolt   is   passed 


i 

B 

= 

\\ 
II 

!! 

Urj 

j 

> 

Fig.  39. 

through  the  base  of  the  device  and  the  nut  then 
put  on  and  screwed  down.  Two  of  these  piers  are 
used  for  each  device. 

Fig.  39  shows  a  crank  fastened  to  its  foundation 
in  each  of  the  three  ways. 

The  first  method  is  little  practiced  now.  The 
tendency  is  to  do  away  with  the  use  of  wood  as 
much  as  possible  at  interlocking  plants. 

The  second  method  allows  of  no  sidewise  adjust- 
ment in  case  the  foundation  should  move,  which  is 
unavoidable  at  times  on  new  fills. 

The  third  method  is  excellent  practice,  although 


90  SAILWAY  SIGNALING 

if  the  nuts  loosen  the  bolt  heads  may  slide  along 
the  grooves  and  allow  the  device  to  move  sidewise 
when  it  should  not.  It  cannot  move  far,  however, 
and  may  easily  be  driven  back  into  place,  and  the 
bolts  tightened  up. 

The  tops  of  all  foundations  should  be  neatly 
finished  off  with  grout.  It  is  generally  a  sign  of  a 
good  foreman  if  he  takes  pains  to  leave  his  founda- 
tions looking  well. 


CHAPTER  VII. 

LOCKING  AND  OPERATING  DEVICES. 

Our  next  step  brings  us  to  the  operation  of 
switches. 

The  simplest  way  to  do  this,  of  course,  is  to  let 
the  pipe  line  which  is  to  operate  the  switch  run 
along  side  of  and  parallel  to  the  track  in  which  the 
switch  is,  and  when  reaching  a  point  opposite  the 
head  rod  of  the  switch,  to  set  a  crank  and  connect 
its  arms,  one  to  the  pipe  line  leading  from  the  ma- 
chine and  the  other  to  the  head  rod  of  the  switch. 
To  a  certain  extent  this  is  the  method  followed. 
However,  it  would  not  be  safe  to  depend  on  this  alone, 
as  the  switch  might  be  600  or  700  ft.  away  from  the 
machine  and  entirely  out  of  sight  of  the  leverman,  and 
as  the  pins,  jaws,  crank  arms,  etc.,  are  wearing  all 
the  time,  enough  lost  motion  is  soon  made  in  the 
pipe  line  to  prevent  the  leverman  detecting  the  presence 
of  some  hard  substance  like  a  stone  between  the 
switch  point  and  the  stock  rail,  which  might  spring 
the  switch  point  enough  open  to  cause  a  derailment. 

The  most  approved  method  of  operating  a  switch 
is  as  follows:  The  pipe  line  is  led  up  to  the  head 
rod  just  as  described.  The  lever  which  operates  a 
switch  gives  the  pipe  line  a  movement  of  8^4  ins. 
which  is  carried  up  to  the  last  crank  arm.  As  the 
throw  of  switches  is  not  often  over  5  ins.  we  want 
to  lose  3^4  ins.  of  stroke  between  the  crank  and 
the  switch  point.  We  could,  of  course,  shorten  one 
crank  arm,  but  the  better  method  is  by  using  what 

91 


92 


RAILWAY  SIGNALING 


is  known  as  a  special  switch  adjustment.  This  is 
an  arrangement  of  a  threaded  rod  fitted  with  nuts  pass- 
ing through  a  socket.  If  the  nuts  are  closed  up  on  the 
ends  of  the  socket  any  movement  imparted  to  the  rod 
will  move  the  socket,  but  if  the  nuts  are  moved  away 
from  the  ends  of  the  socket  any  amount  of  motion 
we  please,  less  than  the  motion  of  the  rod,  will  be 
imparted  to  the  socket.  In  practice  the  nuts  are 
followed  by  jamb  nuts  which  prevent  their  backing 
away  after  being  once  set,  and  the  socket  is  fast- 
ened to  the  head  rod  of  the  switch. 

Fig.  40  shows  a  very  popular  form  of  this  device. 


Fig.  40. 

This  is  intended  to  be  attached  to  the  head  rod  be- 
tween the  two  points  of  the  switch. 

In  addition  to  the  special  switch  adjustment  at- 
tached to  the  head  rod  of  the  switch,  a  front  rod  is 
attached  to  the  points.  This  front  rod  which  is  shown 
in  Fig.  41  is  made  up  of  three  parts;  (i)  the  rod  itself, 
(2)  the  right  hand  point  lug,  (3)  the  left  hand  point 
lug. 


Fig.  41. 

The  point  lugs  are  bolted  to  the  switch  points  so  as 
to  extend  a  little  beyond  their  ends,  and  the  rod  is 
attached  to  each  of  them  so  that  as  the  switch  is  moved 
from  one  of  its  positions  to  the  other,  the  front  rod  is 
given  a  longitudinal  movement  equal  to  the  throw  of 


IN  THEORY  AND  PEACTICE.  93 

the  switch.  In  the  middle  of  the  front  rod  is  a  lug 
projecting  from  its  lower  side,  and  to  this  lug  is  at- 
tached the  lock  rod,  one  type  of  which  quite  com- 
monly used  is  shown  in  Fig.  42.  The  lock  rod  is  up- 
ported  in  the  same  vertical  plane  as  the  front  rod,  and, 
of  course,  moves  longitudinally  backward  and  forward 
with  the  front  rod.  This  lock  rod  is  carried  under 
the  main  rail  of  the  track  in  which  the  switch  is  situ- 
ated, and  its  free  end  which  is  outside  of  the  track 
and  is  a  flattened  bar  of  iron,  is  passed  through  a 
rectangular  hole  in  a  casting  known  as  a  plunger  block 
or  plunger  casting  which  is  bolted  down  to  the  outer 
end  of  the  same  tie  on  which  the  ends  of  the  switch 
points  rest. 


Fig.  42. 

.  Cast  in  this  plunger  block  and  at  right  angles  to  the 
rectangular  hole  through  which  the  lock  rod  slides 
back  and  forth,  but  in  a  horizontal  plane  passing 
through  the  center  line  of  the  outside  end  of  the  lock 
rod,  is  a  round  hole  in  which  a  smooth  steel  pin  called 
the  plunger  can  slide  backward  and  forward  at  right 
angles  to  the  line  of  travel  of  the  lock  rod. 

The  end  of  the  plunger  which  does  not  enter  into 
the  plunger  block  is  shaped  into  an  eye  by  which  it  is 
attached  by  a  jaw,  preferably  a  screw  jaw,  to  a  pipe 
line  leading  to  a  lever  in  the  machine,  different  from 
the  one  by  which  the  switch  is  moved,  and  so  con- 
nected that  when  the  lever  is  reversed  the  plunger  will 
be  shoved  forward  in  the  plunger  block,  and  when  the 
lever  is  set  normal  again  it  will  be  withdrawn  until  its 
end  clears  the  rectangular  hole  in  which  the  lock  rod 
travels. 

Now  if  two  holes   tTie  same  diameter  or  a  little 


94  RAILWAY  SIGNALING 

larger  than  the  plunger  are  drilled  in  the  lock  rod  so 
that  when  the  switch  is  in  its  normal  position  one  of 
them  will  be  exactly  opposite  the  round  hole  in  the 
plunger  block,  and  the  other  one  so  that  it  will  occupy 
that  position  when  the  switch  is  reversed,  it  is  easily 
seen  that  when  the  lock  lever  is  reversed  the  plunger 
will  pass  through  the  hole  in  the  lock  rod  and  thereby 
lock  the  switch  in  either  position  it  may  be  in  at  the 
time,  but  if  the  switch  has  not  made  all  of  its  travel 
so  as  to  close  up  against  the  stock  rail,  the  end  of  the 
plunger  will  strike  against  the  side  of  the  lock  rod 
where  there  is  no  hole,  and  as  it  can  then  go  no  far- 
ther the  leverman  will  be  unable  to  get  the  lock  lever 
all  the  way  over  and  will  know  that  there  is  something 
wrong  at  the  switch.  This  arrangement  is  known  as  a 
facing  point  lock,  and  a  good  deal  more  will  be  said 
about  it  before  we  are  through. 

The  use  of  the  facing  point  lock  makes  it  as  certain 
as  human  ingenuity  has  yet  been  able  to  make  it,  that 
a  switch  is  safe  for  the  passage  of  a  train,  but  there  is 
one  contingency  that  the  lock  in  itself  does  not  pro- 
vide against.  This  is,  that  a  leverman  may,  thinking 
that  a  train  has  passed  entirely  over  a  switch,  unlock 
it  and  then  throw  it  between  the  trucks  of  an  engine 
or  car,  thereby,  if  it  happens  to  be  a  facing  point 
switch,  causing  a  derailment.  To  prevent  this,  what  is 
known  as  the  detector  bar  has  been  designed.  This 
is  a  flat  bar  of  iron  ^  in.  by  2%  in.  or  */£  in.  by  2>4 
in.,  with  a  bevelled  edge  and  generally  50  ft.  long, 
although  there  is  a  tendency  at  present  to  make  them 
53  ft.  long.  This  is  supported  along  the  outside  edge 
of  one  rail  or  the  other  immediately  in  advance  of  the 
switch  points.  It  is  carried  by  supports  attached  to 
the  rail,  so  arranged  that  as  the  bar  slides  backward 
and  forward  along  the  side  of  the  rail,  it  is  raised  up 
and  then  lowered  again.  This  bar  is  attached  to  the 
same  pipe  line  that  moves  the  plunger,  so  that  every 


IN  THEORY  AND  PRACTICE. 


95 


time  the  plunger  is  moved  back  or  forth  the  detector 
bar  is  raised  and  lowered.  The  wheels  of  engines  and 
cars  being  wider  than  the  tops  or  "heads"  of  the  rails, 
as  long  as  a  wheel  is  over  the  detector  bar,  it,  the  bar, 
cannot  rise  enough  to  allow  the  switch  to  be  unlocked, 
and  its  length  is  such  that  no  equipment  used  on 
American  railroads  has  enough  space  between  its 
trucks  to  allow  a  bar  to  be  thrown  between  them.  The 
supports  for  the  detector  bar  are  known  as  rail  clips. 
There  are  a  good  many  designs  of  these.  One  kind 


Fig.  43. 

operates  by  a  link  which  is  the  radius  of  the  sector  of  a 
circle,  and  the  other  is  a  cam  arrangement. 

As  it  is  extremely  important  that  the  track  at  the 
switch  points  of  an  interlocked  switch  should  be  kept 
to  its  true  gauge,  it  is  the  general  practice  to  provide 
a  plate  of  iron  about  6  ft.  10  in.  long,  which  is  screwed 
or  bolted  down  to  the  top  of  the  tie  on  which  the  ends 
of  the  switch  points  rest,  and  to  one  end  of  which  the 
plunger  block  is  fastened.  This  plate  known  as  the 
tie  plate,  has  strips  riveted  across  it  against  which  rail 
braces  are  placed,  thereby  making  a  very  strong  sup- 
port against  spreading  of  the  rails.  Fig.  43  is  a  plan 
of  a  switch  fitted  up  as  above,  showing  all  the  parts 
mentioned  and  also  a  bolt  lock,  the  use  of  which  will 


96 


BAILWAY  SIGNALING 


be  described  further  on  when  we  get  to  signal  move- 
ments. 

There  are  times  when  it  is  impossible  to  run  the 
detector  bar  ahead  of  the  switch,  as  for  instance,  in  a 
case  where  the  switch  is  within  ten  feet  of  a  railroad 
crossing,  or  a  paved  street.  In  such  cases  two  detec- 
tor bars  are  used,  one  on  either  rail  back  of  the  points. 
Fig.  44  illustrates  a  typical  arrangement  of  this  sort. 

There  is  another  locking  arrangement  known  as  a 
switch  and  lock  movement  which  is  sometimes  used. 
With  this  the  same  pipe  line  which  throws  the  switch 
also  operates  the  lock  and  detector  bar.  This  device 


Fig.  44. 

is  very  ingenious.  Its  main  feature  is  an  escapement 
crank,  which  is  a  crank  one  arm  of  which  is  shaped 
into  a  cam.  This  cam  is  so  arranged  that  the  first 
one-third  of  the  lever  stroke  will  not  move  the  crank 
at  all,  the  second  one-third  gives  the  crank  its  full 
throw,  and  the  last  third  again  does  not  move  the 
crank.  By  having  the  crank  throw  the  switch  and 
the  last  third  of  the  stroke  lock  it  and  lower  the  de- 
tector bar,  we  have  the  complete  device.  When  the 
movement  is  reversed  the  first  third  of  the  stroke 
(which  was  the  last  third  in  the  other  movement) 
unlocks  the  switch  and  raises  the  detector  bar,  the 


IN  THEORY  AND  PRACTICE. 


97 


middle  third  throws  it,  and  the  last  third  locks  it  again, 
and  drops  the  detector  bar. 

There  is  more  than  one  method  of  constructing 
these  devices,  but  the  type  most  generally  used  at  the 
present  time  is  shown  in  Fig.  45. 

The  slide  bar  is  attached  to  the  pipe  line  from  the 
lever,  and  moves  longitudinally  as  the  lever  is 
moved.  It  is  built  up  of  two  plates,  better  seen  in 
the  side  view,  between  which  is  a  thimble  through 
which  a  pin  connecting  the  two  plates  passes.  As  the 


Fig.  45. 

slide  bar  moves  back  and  forth  this  thimble  rolls  along 
the  edge  of  the  cam  end  of  the  escapement  crank, 
moving  the  crank  as  described  above,  and  thereby 
throwing  the  switch.  On  the  inner  side  of  each  of  the 
plates  forming  the  slide  bar  a  flat  dog  is  riveted.  The 
lock  rod  passes  through  the  rectangular  hole  near  the 
end  of  the  frame  of  the  switch  and  lock  movement. 
Instead  of  having  holes  drilled  in  it,  the  lock  rod  has 
notches  cut  in  its  upper  and  lower  edges  just 
large  enough  for  the  dogs  to  pass  through.  When 
the  slide  bar  is  in  its  normal  position  one  of  these 


98 


RAILWAY  SIGNALING 


dogs  engages  the  lock  rod,  holding  the  switch 
locked.  As  the  slide  bar  is  reversed  the  dog  is  with- 
drawn from  engagement  with  the  lock  rod,  thereby 
unlocking  the  switch,  which  remains  unlocked  for  the 
middle  third  of  the  travel  of  the  slide  bar,  during 
which  time  the  escapement  crank  is  put  in  motion, 
thereby  throwing  the  switch.  The  final  third  of  the 
slide  bar's  travel  moves  the  other  dog  into  engage- 
ment with  the  other  notch  in  the  lock  rod,  thus  again 
locking  the  switch  in  its  reversed  position. 

When  the  lever  is  set  normal  again  this  process  is 
repeated  in  the  opposite  direction. 

Fig.  46  shows  a  switch  with  detector  bar  ahead  of 


Fig.  46. 

the  points,  fitted  with  a  switch  and  lock  movement.  It 
should  be  noted  that  in  all  essential  particulars  the  fit- 
ting up  of  the  switch  as  regards  the  special  switch 
adjustment,  tie  plate,  rail  braces,  front  rod,  lock  rod 
and  detector  bar,  is  the  same  as  for  the  facing  point 
lock.  It  will  hardly  be  worth  while,  therefore,  to  illus- 
trate a  switch  fitted  with  two  detector  bars  back  of  the 
points  and  operated  by  a  switch  and  lock  movement. 
Besides  operating  ordinary  switches,  interlocked 
levers  are  often  called  on  to  operate  slip  switches  and 


IN  THEORY  AND  PRACTICE. 


99 


.Fig.  47. 


Fig.  48. 


100  SAILWAY  SIGNALING 

movable  point  crossings.  There  is  no  essential  differ- 
ence between  the  arrangements  for  this  work  and  for 
work  already  described,  although  the  application  of  the 
several  parts  varies  somewhat.  Fig.  47  shows  a  mov- 
able point  crossing  and  Fig.  48  a  double  slip  switch 
arranged  to  be  operated  by  the  levers  of  an  interlock- 
ing machine.  Facing  point  locks  should  always  be 
used  in  such  cases  to  lock  the  points  and  not  switch 
and  lock  movement.  In  these  Figs,  it  should  be  noted 
that  a  rocker  shaft  is  run  under  the  track  connecting 
the  detector  bars  on  the  two  sides  and  causing  them 
to  work  simultaneously.  This  arrangement  is  also 
very  convenient  at  times  where  there  is  limited  room 
to  set  cranks,  with  switches  which  are  double  barred. 

It  is  customary  to  provide  large  oak  timbers  to  sup- 
port the  mechanisms  at  switches  and  derails.  Oak,  ten 
inches  by  ten  inches,  and  twelve  feet  long,  is  a  very 
convenient  size  for  this  purpose.  With  switch  and  lock 
movements  at  least  three  pieces  should  be  used — one 
for  the  three-way  crank,  one  for  the  tie  plate  under 
the  points  of  the  switch,  and  one  in  place  of  the  first 
tie  back  of  the  switch  points  to  support  the  other  end 
of  the  switch  and  lock  movement  base.  The  tie-plate 
timber  may  be  made  narrower  than  the  other  two,  but 
it  is  just  as  well  to  use  the  same  size  throughout  and  to 
adze  down  the  sides  of  this  timber  so  as  to  make  it  the 
same  width  as  the  tie  plate  on  top.  This  is  necessary 
in  order  to  clear  the  special  switch  adjustment. 

With  facing  point  locks,  two  timbers  are  enough, 
one  to  support  the  plunger  casting  and  one  to  support 
the  three-way  crank,  unless  a  bolt  lock  is  put  on  the 
ties,  when  a  third  timber  may  be  put  in  to  support  it. 
As  a  rule,  however,  it  is  more  convenient  to  support 
the  bolt  lock  on  a  concrete  foundation.  Some  signal 
engineers  use  more  timbers  than  I  have  specified,  but 
I  think  my  list  is  enough. 


CHAPTER  VIII. 

SIGNALS — BOLT    LOCKS — SELECTORS — MECHANICAL 
SLOTS. 

Our  next  step  brings  us  to  signal  movements,  and 
we  will,  of  course,  discuss  those  operated  by  pipe  lines, 
"pipe  connected"  signals,  first. 

It  is  now  the  universal  practice  to  use  iron  signal 
masts  for  high  signals.  At  one  time  these  were  set 
by  being  raised  in  a  large  hole  dug  to  receive  their 
lower  end,  which  was  afterwards  filled  in  with  con- 
crete. During  the  last  few  years,  however,  the  sig- 
nals have  been  made  with  a  large  cast  iron  base,  so 
that  they  stand  on  top  of  the  concrete  foundation,  and 
are  fastened  thereto  by  strong  hook  bolts  which  are 
embedded  in  the  foundation.  Dwarf  signals  have  al- 
ways been  made  of  iron,  and  like  the  high  signals  are 
bolted  to  a  concrete  foundation,  which,  of  course,  does 
not  require  to  be  as  large  as  the  foundation  of  the 
high  signal. 

High  signals  consist  of  the  base;  the  pole,  which  is 
made  of  three  lengths  of  pipe  6^  in.,  5  9-16  in.  and 
4^/2  in.  outside  diameter  respectively  (these  are  most 
frequently  swaged  together  at  the  joints)  ;  the  pin- 
nacle which  is  a  cast  iron  cap  to  fit  over  the  top  of  the 
pole  and  keep  rain  and  snow  from  getting  inside  of  it, 
as  well  as  to  give  it  a  neat  appearance ;  the  arm  plate, 
sometimes  called  the  spectacle  casting,  which  is  a  cast 

101 


102  KA1LWAY  SIGNALING 

iron  plate  with  holes  cast  near  one  edge  in  which  the 
colored  glasses  or  roundels  which  give  the  night  indi- 
cations are  fixed,  and  a  socket  in  the  opposite  edge  to 
which  the  blade  is  bolted. 

This  arm  plate  is  fitted  on  a  square  shank  at  the  end 
of  a  turned  axle  called  the  spindle,  which  is  supported 
in  a  casting  called  the  arm  plate  bearing,  which  is  bolt- 
ed to  the  pole  near  its  top. 

Generally  a  back  light  casting,  of  which  more  will 
be  said  later  when  we  come  to  night  indications,  is 
fastened  to  the  other  end  of  the  spindle.  An  ironA lad- 
der is  attached  to  the  pole,  so  that  persons  may  climb 
it  to  put  up  or  take  down  the  lamps,  and  to  make  re- 
pairs. 

Near  the  base  of  the  pole,  sometimes  a  part  thereof, 
is  another  casting  to  which  a  crank  or  chain  wheel 
may  be  bolted.  The  ladder,  too,  is  stayed  to  the  pole 
to  steady  it. 

With  pipe  connected  high  signals,  a  crank  with  one 
arm  much  longer  than  the  other,  known  as  an  "L" 
crank  or  counter  weight  lever  is  bolted  to  the  base  or 
casting  just  above  the  base.  The  long  arm  of  this  "L" 
crank  has  a  hole  drilled  in  it  a  few  inches  from  the 
hub.  A  screw  jaw  tanged  to  fit  %  in.  instead  of  1-in. 
pipe,  is  pinned  to  the  crank  through  this  hole,  and  a 
24-in.  pipe  called  the  up  and  down  rod  is  carried  up  to 
the  arm  plate  parallel  to  the  pole. 

This  up  and  down  rod  is  attached  to  a  pin  in  the 
arm  plate  by  an  eye  rod  tanged  on  its  down  end  to 
receive  the  pipe.  The  up  and  down  rod  is  steadied 
by  wrought  iron  guides  clamped  around  the  pole. 

A  heavy  cast  iron  weight  with  a  hole  cored  through 
it  to  receive  the  crank  arm,  called  the  counter  weight, 
is  passed  over  the  end  of  the  long  arm  of  the  "L" 
crank  and  held  by  a  set  screw.  The  spindle,  around 
whose  center  the  arm  plate  revolves  is  so  arranged  as 


IN  THEOBY  AND  PRACTICE.  103 

•< 

to  be  between  the  pin  to  which  the  up  and  down  rod  is 
attached  and  the  semaphore  arm.  The  force  of  gravity 
acting  on  the  counter  weight  pulls  down  on  the  up  and 
down  rod,  which  in  turn  transmits  this  pull  to  the  end 
of  the  arm  plate  to  which  it  is  attached,  and  conse- 
quently raises  up  the  end  to  which  the  blade  is  attached, 
thereby  always  tending  to  bring  the  blade  into  the 
horizontal  position. 

Fig.  49  shows  a  front  and  side  view  of  a  high  home 
signal. 

The  Fig.  shows  a  one-bladed  signal.  In  a  two  or 
three-bladed  signal  the  upper  length  of  pipe  in  the 
pole  is  extended,  and  the  additional  arm  plate  bear- 
ings, arm  plates  and  blades  are  attached  as  is  done 
with  the  one-bladed  signal.  The  "L"  crank  is  made  in 
two  or  three  "ways,"  and  an  additional  up  and  down 
rod  is  put  on  for  each  blade.  The  lowest  blade  should 
be  25  ft.  from  the  top  of  the  foundation,  and  other 
blades  are  spaced  6  ft.  6  in.  therefrom  and  from  each 
other. 

Fig.  50  shows  a  front  and  side  view  of  a  typical  pipe 
connected  dwarf  signal.  The  ladder  is,  of  course,  un- 
necessary with  these  as  they  are  generally  less  than 
three  feet  high.  Neither  is  it  necessary  to  guide  the 
up  and  down  rod.  In  other  essential  particulars  they 
are  much  the  same  as  the  high  signals. 

In  Figs.  49  and  50  the  signals  shown  are  of  the  two 
position  type,  60  degrees  downward  inclination. 

A  three-position,  either  lower  or  upper  quadrant 
signal,  is  made  by  applying  an  arm  plate  bearing  and 
arm  plate  of  a  slightly  different  design.  The  other 
fittings  remain  the  same.  The  reader  should  note  that 
there  are  three  holes  for  glass  in  the  arm  plate  illus- 
trated for  the  high  signal,  and  two  in  the  arm  plate 
illustrated  for  the  dwarf.  The  reason  for  this  will  be 
explained  fully  when  we  come  to  night  indications. 

The    pipe    line    leading    from    the    lever    in    the 


104 


RAILWAY  SIGNALING 


Fig.  49. 


tower  is  led  up 
to  the  signal 
and  attached  by 
a  jaw  to  the 
short  arm  of  the 
"L"  crank.  It 
is  good  practice 
to  use  a  screw 
jaw  for  this 
connection,  as 
it  is  often  con- 
venient  to 
lengthen  or 
shorten  the 
pipe  line  a  little 
at  the  base  of 
the  signal. 

We  will  now 
return  to 
switch  m  o  v  e- 
ments  for  a  mo- 
ment, and  ex- 
plain the  use  of 
bolt  locks  to 
which  we  have 
referred. 

In  England 
these  devices 
are  called  "de- 
tectors," which 
is  perhaps  a 
more  explana- 
tory title  than 
that  of  bolt 
lock. 

Their  object  is 
to  prevent  the 
leverman  from 


IN  THEORY  AND  PRACTICE. 


105 


clearing  a  signal  if  the  switch  which  it  governs  has 
failed  to  respond  to  the  movement  of  its  lever.  For 
instance,  we  will  suppose  that  the  pipe  line  operating  a 
switch  several  hundred  feet  away  from  the  tower  has 
broken  close  to  its  connection  with  the  switch.  The 
leverman  reverses  his  lever  and  the  drag  of  the  pipe 
line  is  heavy  enough  to  prevent  his  detecting  that  the 
switch  has  failed  to  respond  to  the  lever  movement. 
He  might  then  reverse  his  facing  point  lock  lever  and 


Fig.  50. 

the  plunger  would  enter  the  hole  in  the  lock  rod  for 
the  switch  in  its  normal  position  and  he  would  still  fail 
to  discover  that  the  switch  had  not  moved.  He  could 
then  clear  his  signal,  thereby  giving  wrong  and  perhaps 
dangerous  information  to  the  engineman  of  an  ap- 
proaching train.  Where  a  bolt  lock  is  used,  this  can- 
not be,  as  will  now  be  shown. 

The  bolt  lock  Fig.  51  consists  of  two  rectangular 
bars  of  iron,  free  to  move  longitudinally  in  a  cast  iron 
frame,  and  so  placed  that  they  cross  each  other  at  right 
angles,  with  the  center  line  of  one  a  little  above  that 
of  the  other.  Each  of  these  bars  has  a  notch  about 
half  its  width  cut  in  one  of  its  edges.  One  of  them  is 


106 


RAILWAY  SIGNALING 


attached  to  the  switch  points,  usually  to  the  point  lug 
on  the  side  nearest  the  pipe  line  to  the  signal  and  is 
called  the  switch  bar,  and  the  other  is  cut  into  the  pipe 
line  which  operates  the  signal  itself,  and  is  called  the 
signal  bar.  The  switch  bar,  of  course,  moves  back- 
ward and  forward  as  the  switch  is  thrown,  just  as  has 
already  been  described  for  the  lock  rod,  provided,  and 
here  is  the  essential  point,  that  the  notch  in  the  signal 
bar  is  in  the  same  vertical  plane  in  which  it,  the  switch 
bar,  travels.  The  signal  bar  too  can  only  make  its 


Fig.  51. 


travel  when  the  notch  in  the  switch  bar  is  in  the  same 
vertical  plane  in  which  it  travels.  With  the  signal 
normal  (in  the  stop  position)  the  signal  bar  is  so 
placed  that  its  notch  will  allow  free  movement  to  the 
switch  bar. 

In  the  case  we  have  just  cited,  however,  the  notch 
in  the  switch  bar  would  not  move  into  the  same  ver- 
tical plane  in  which  the  signal  bar  moves  until  the 
switch  had  been  reversed,  and  the  signal  could  not, 
therefore,  be  cleared  because  the  edge  of  the  notch  in 
the  signal  bar  would  strike  against  the  unnotched  side 
of  the  switch  bar.  Therefore,  if  the  switch  had  failed 


IN  THEORY  AND  PRACTICE.  107 

to  move  when  its  lever  was  reversed,  the  signal  could 
not  be  cleared,  because  its  pipe  line  would  be  prevented 
from  moving  by  the  bolt  lock  and  the  leverman  fail- 
ing in  his  efforts  to  reverse  the  signal  lever  would  be 
warned  that  the  switch  had  not  moved. 

Next  to  the  interlocking  of  the  levers  in  the  machine, 
this  device  is  probably  the  greatest  safeguard  in  the 
construction  of  a  mechanical  interlocking  plant,  and 
every  high  speed  facing  point  switch  should  be  bolt 
locked  with  every  signal  controlling  the  route  over  it. 
Bolt  locks  are  made  in  one,  two  or  three  "ways,"  so 
that  a  switch  may  lock  one  signal  in  its  normal  posi- 
tion, and  another  one  or  two  in  its  reversed  position, 
or  vice  versa. 

Fig.  52  shows  a  wire  connected  high  signal.  It  will 
be  noted  that  instead  of  the  "L"  crank  a  tandem  chain 
wheel  is  attached  to  the  foot  of  the  pole. 

The  two  wires  from  the  lever  have  pieces  of  one- 
quarter  inch  straight  link  chain  let  into  them,  which 
are  passed  around  these  chain  wheels.  From  the 
other  end  of  the  chains  the  wires  are  continued  and 
connect  to  a  balance  lever  placed  more  than  half  way 
up  the  pole. 

On  one  end  of  this  balance  lever  is  a  counter  weight, 
and  a  short  up  and  down  rod  connects  it  to  the  arm 
plate.  When  the  lever  in  the  tower  is  reversed  the 
wire  connected  to  the  end  of  the  balance  lever  farthest 
away  from  the  counter  weight  is  pulled  on,  while  the 
other  is  slacked  away.  This  raises  the  counter  weight, 
shoves  up  on  the  up  and  down  rod,  and  brings  the 
signal  blade  to  the  clear  position.  When  the  lever  is 
returned  to  normal  the  other  wire  is  pulled  on,  while 
the  first  one  mentioned  is  slacked  away,  pulling  down 
the  counter  weight  and  raising  the  blade  to  its  normal 
position.  It  is  intended  that  the  counter  weight  should 
be  heavy  enough  to  restore  the  blade  to  normal,  unas- 
sisted, but  it  has  been  found  to  be  much  better  to  also 


108 


RAILWAY  SIGNALING 


Fig.  52. 


have  a  pull  on  the  balance 
lever,  hence  the  second 
wire  has  been  introduced. 
In  early  installations  in 
this  country,  only  one  wire 
was  used,  and  the  signal 
was  returned  to  normal 
by  the  counter  weight 
alone,  but  there  is  too 
much  chance  of  a  kink  in 
the  wire  catching  in  a 
wire  pulley  and  holding 
the  signal  at  clear  for  this 
method  to  be  continued  as 
good  practice. 

In  England  one  wire 
only  is  used  at  the  pres- 
ent time,  but  there  a 
small,  very  flexible  wire 
cable  is  used  instead  of 
the  hard  drawn  steel  wire 
used  in  America,  and  the 
chances  of  its  kinking  are 
not  so  great. 

Fig-  53  shows  a  very 
common  type  of  wire  con- 
nected dwarf  signal.  Here 
the  pull-to-clear  wire  is 
carried  around  a  horizon- 
tal chain  wheel  and  then 
to  the  end  of  the  operat- 
ing shaft,  while  the  wire 
from  the  tail  lever  in  the 
tower  is  attached  directly 
to  the  end  of  the  operat- 
ing shaft.  When  the  lever 
is  reversed  the  operating 


IN  THEORY  AND  PRACTICE. 


109 


shaft  is  pulled  towards  the  right  of  the  figure  com- 
pressing the  coil  spring  which  is  wound  around  it. 
A  projection  from  the  end  of  the  operating  shaft  en- 
gages the  escapement  crank,  which  shoves  up  on  the 
up  and  down  rod  and  clears  the  signal  blade.  The 
spring  in  this  type  takes  the  place  of  the  counter  weight 
in  the  high  signal. 

Bolt  locks  may  be  used  with  wire  connected  signals 
as  with  pipe  connected.    The  signal  bar  in  a  wire  bolt 


Fig.  53. 

lock  is  equipped  with  shackles  on  each  end,  instead  of 
tangs.  Where  a  bolt  lock  is  cut  in  to  a  wire^  line,  it 
should  always  be  in  the  wire  which  pulls  the  signal  to 
clear. 

I  will  digress  here  a  moment  to  say  that  amongst 
signal  men  the  wire  which  pulls  the  signal  to  clear  is 
usually  called  the  front  wire,  and  the  one  which  pulls 
it  to  normal,  the  back  wire.This  nomenclature  is  a  lit- 


110  RAILWAY  SIGNALING 

tie  confusing  to  a  beginner,  because  the  front  wire  is 
attached  to  what  in  the  machine  is  the  back  of  the 
lever,  and  the  back  wire  to  the  front  of  the  lever.  I 
avoided  the  use  of  the  terms  front  and  back  wire  in 
the  foregoing  description  just  for  that  reason,  but 
hereafter  when  I  have  occasion  to  mention  these  wires 
I  will  call  them  front  and  back  in  the  sense  just  ex- 
plained. 

Wire  adjusting  screws  should  be  let  into  both  the 
front  and  back  wires  near  the  signal,  either  high  or 
dwarf,  in  addition  to  those  in  the  tower. 

In  the  foregoing  description  I  have  purposely  omit- 
ted reference  to  bracket  signals.  I  shall  now  say  a 
few  words  on  that  subject.  The  attachments,  or  as 
they  are  generally  called,  "fittings"  for  bracket  signals 
do  not  differ  greatly  from  those  already  described. 
With  pipe  connected  signals  the  "L"  cranks  are  placed 
at  the  base  of  the  pole.  The  up  and  down  rods  are 
run  up  the  pole  to  the  bracket  where  they  are  pinned 
by  jaws  to  right  angle  cranks  which  connect  by  hori- 
zontal pipe  lines  to  other  right-angle  cranks  at  the 
base  of  the  "masts"  which  again  turn  the  direction  of 
the  pipe  to  vertical  and  connect  to  the  arm  plate. 

With  wire  connected  signals  a  tandem  chain  wheel 
is  placed  at  the  bracket  and  the  wires  connect  to  a 
balance  lever,  the  end  of  which  is  made  like  a  three 
way  crank.  Another  tandem  chain  wheel  is  placed  at 
the  base  of  the  pole. 

Fig.  54  shows  a  pipe  and  Fig.  55  a  wire  connected 
bracket  signal  from  which  the  reader  will  easily  see  at  a 
glance  how  the  connections  are  made.  The  main  poles 
of  bracket  signals  are  not  infrequently  made  by  a  lat- 
tice method  of  construction  and  not  of  large  pipe. 
The  masts,  however,  are  always  made  of  pipe. 

I  shall  now  describe  another  device,  which,  although 
it  is  not  used  to  any  great  extent  in  modern  signal 
practice,  and  should  certainly  be  avoided  in  new  work 


IN  THEORY  AND  PRACTICE.  Ill 


Fig.  54. 


112 


•RAILWAY  SIGNALING 


Fig.  55. 


IN  TREORY  AND  PRACTICE. 


113 


as  much  as  possible,  is  a  very  handy  device  at  times 
where  old  plants  are  to  be  enlarged.  It  is  known  as  a 
selector.  By  its  use  one  lever  may  be  made  to  throw 
one,  two,  three,  or  even  four  signal  blades,  each  inde- 
pendently of  the  other.  A  switch  must,  however,  enter 
into  the  combination. 

We  will  take  the  case  of  a  two-arm  pipe  connected 
home  signal  governing  the  two  routes  at  a  junction. 
The  pipe  line  from  one  lever  in  the  machine  would  be 
led  up  to  the  selector,  which  is  placed  near  the  signal. 
If  the  switch  is  normal  the  ipe  line  will  be  attached 


Fig.  56. 

through  the  selector  to  one  signal  arm,  but  if  the 
switch  is  reversed  the  pipe  line  will  be  detached  from 
that  arm  and  attached  to  the  other.  The  switch  selects 
its  signal,  hence  the  name. 

Fig.  56  shows  a  common  design  of  three  way,  or^as 
it  is  more  often  called,  three  hook  selector,  in  which 
escapement  cranks  are  rigidly  fastened  to  rods.  These 
escapement  cranks  are  operated  by  lugs  attached 
to  the  pipe  line  by  which  the  switches  which  do  the 
selecting  are  moved.  As  either  of  these  pipe  lines 


114 


EAILWAY  SIGNALING 


move  it  also  moves  the  escapement  crank,  which  in 
turn  revolves  the  rod  to  which  it  is  attached.  This 
rod  also  has  a  cam  attached  to  it,  which  as  it  revolves, 
either  lowers  or  raises  one  of  the  hinged  hooks, 
shown  in  the  Fig.  When  down  these  hooks  engage 


IT-TV  Tn 


the  slide,  which  by  its  tanged  end  is  fastened  to  the 
pipe  line  leading  from  the  signal  lever.  A  movement 
of  this  pipe  line,  therefore,  moves  any  one  of  the  three 
pipe  lines  whose  hook  happens  to  be  down  at  the  time. 
Each  of  the  three  is  attached  to  a  different  signal 


IN  THEORY  AND  PRACTICE.  115 

blade,  so  that  as  before  explained  the  position  of  the 
switch  selects  the  signal  which  the  lever  will  operate. 

One  serious  trouble  with  pipe  selectors  is  that  ice 
and  snow  sometimes  pack  in  to  them  so  that  the  hooks 
cannot  drop  down  and  hold  in  the  slide. 

Pipe  selectors  should  be  placed  near  the  signal  so 
as  to  save  as  much  pipe  line  as  possible. 

The  most  favored  type  of  wire  selector  is  the  tower 
type,  shown  in  Fig.  57.  With  this  separate  wire  lines 
of  one  wire  each  are  run  from  the  signals  to  the  tower, 
and  the  selector  is  placed  in  its  lower  story. 

Only  one  back  wire  is  used  which  is  attached  to  the 
tail  lever  of  the  signal  lever.  The  balance  lever  on  the 
signal  pole  is  made  in  as  many  ways  as  there  are 
signal  blades  to  operate.  A  short  chain  is  passed 
through  a  loose  pulley,  with  a  hook  on  the  end  to 
which  the  back  wire  is  attached,  and  the  two  ends  of 
the  chain  are  fastened  to  the  outside  and  inside  bal- 
ance levers,  after  being  looped  through  large  shackles 
on  the  intermediate  balance  levers.  When  the  signal 
lever  is  reversed  the  back  wire  is  slacked  away  and  the 
balance  lever  which  is  pulled  down  by  the  front  wire 
pulls  up  enough  slack  chain  through  the  movable  pul- 
ley in  completing  its  stroke,  to  draw  the  back  wire 
fairly  taut.  When  the  signal  lever  is  returned  to  nor- 
mal and  the  back  wire  pulled  on,  it  will  draw  down 
enough  on  the  balance  lever  to  insure,  being  aided  by 
the  counter  weight,  that  the  signal  blade  is  returned 
to  normal.  The  tower  ends  of  the  front  wires  are  at- 
tached to  the  lower  ends  of  the  selector  hooks. 

The  movements  of  the  switch  levers  revolve  the 
short  rocking  shafts  or  bars  to  which  they  are  attached 
which  carry  the  cams  with  them  and  engage  or  dis- 
engage the  proper  selector  hooks  to  or  from  the  slide 
plate,  which  is  attached  to  the  back  of  the  signal 
lever  much  the  same  as  already  described  for  the 
pipe  selector.  The  whole  device  being  inside  the 


116 


RAILWAY  SIGNALING 


tower  is  not  subject  to  interference  from  ice  and  snow 
as  is  the  case  with  a  pipe  selector.  As  this  type  stands 
vertically  in  the  tower  the  force  of  gravity  cannot  be 
depended  on  to  drop  the  hooks  into  place.  Their  lower 
ends  are  so  shaped  that  the  weight  of  the  front  wire 
which  they  support  tends  always  to  draw  the  hook  end 
in  toward  the  slide. 


Fig.  58. 


Another  device  which  is  the  opposite  of  a  selector 
is  the  mechanical  slot.  Its  use  makes  it  necessary  for 
two  levers  to  be  reversed  in  order  to  clear  one  signal. 
It  is  very  little  used  at  present  on  complete  interlock- 
ing plants  for  reasons  which  will  appear  later  when 


IN  THEORY  AND  PRACTICE.  117 

we  come  to  the  consideration  of  power  distant  signals, 
but  is  a  device  which  may  be  made  very  useful  where 
switches  which  are  operated  by  ordinary  switch  stands 
are  bolt  locked  with  a  signal.  This  will  be  taken  up 
in  its  proper  place. 

Where  mechanical  slots  are  used  with  complete  in- 
terlocking plants,  it  is  when  two  plants  are  so  near 
each  other  that  one  distant  signal  will  suffice  for  both, 
the  action  of  the  device  being  so  that  if  leverman  at 
A  sets  the  switches,  derails  and  home  signal  for  a 
route  and  reverses  his  distant  signal  lever  the  blade 
will  not  respond  thereto  unless  leverman  at  B  has  also 
set  his  switches,  derails  and  home  signal  and  reversed 
his  distant  signal  lever. 

Fig.  58  shows  one  design  of  mechanical  slot.  It  is 
generally  attached  to  the  signal  pole  above  the  balance 
lever.  The  balance  lever  is  a  two  way,  and  the  levers 
are  attached  to  the  vertical  slides,  shown  as  a  a'  in 
the  figure.  The  slot  slide  b  is  attached  to  the  arm 
plate  of  the  signal  blade  by  a  short  up  and  down  rod. 
When  A  reverses  his  lever  vertical  slide  a  moves  up- 
ward past  roller  c,  shoving  it,  the  roller,  to  one  side 
and  does  not  move  the  slot  slide  or  signal  blade. 

If,  however,  after  A  has  reversed  his  lever,  B 
should  reverse  his,  roller  c  cannot  move  out  of  the 
way  of  vertical  slide  a'  to  which  B's  lever  is  attached. 
Consequently  the  vertical  slide  shoves  up  on  the  roller 
and  through  it  on  the  slot  slide  and  arm  plate,  thereby 
clearing  the  signal.  If  B  should  reverse  his  lever  first 
the  action  of  the  slot  would  simply  be  reversed,  and 
the  signal  arm  would  not  be  moved  until  A  had  re- 
versed his  lever. 

With  both  A's  and  B's  levers  reversed  and  the  sig- 
nal blade  clear,  if  either  sets  his  lever  normal  again, 
roller  c  will  either  roll  away  sideways  from  on  top  of 
the  slide  which  has  shoved  the  signal  to  clear,  or  if 
the  lever  controlling  that  slide  is  the  first  one  to  be 


118  EAILWAY  SIGNALING 

reversed,  it  will  simply  follow  the  end  of  that  slide 
downward  by  the  force  of  gravity.  In  either  case  it 
will  drop  away  from  the  top  of  the  slot  slide,  which 
being  a  fairly  heavy  casting,  acts  as  a  counter  weight 
and  pulls  down  on  the  arm  plate,  restoring  the  signal 
to  the  normal  position. 


CHAPTER  IX. 

DERAILS — GENERAL    REMARKS   ON    MECHANICAL   INTER- 
LOCKING. 

In  the  foregoing  description  of  mechanical  operating 
and  locking  devices  and  lead  outs,  I  have  aimed  as 
much  as  possible  to  avoid  confusing  the  reader  with 
references  to  special  devices  until  the  fundamental 
principles  were  made  clear,  and  to  that  end  have  made 
but  one  allusion  to  derails  so  far.  I  will  now  say  a  few 
words  on  that  head. 

As  a  general  question,  a  derail  movement  is  the 
same  as  that  for  a  switch,  either  a  facing  point  lock  or 
a  switch  and  lock  movement,  but  they  differ  from 
switch  movements  in  one  or  two  minor  details. 

Derails  may  be  grouped  under  three  general  heads : 

(1)  Split  point  derails. 

(2)  Wharton  derails. 

(3)  Solid  derails. 

Fig.  59  shows  I  and  3,  and  Fig.  60  shows  2. 

As  there  is  no  head  rod  to  the  split  point,  and  solid 
type,  a  special  switch  adjustment  such  as  has  been  de- 
scribed for  switch  movements  cannot  be  applied. 
Neither  can  we  use  a  front  rod. 

I  have  found  it  very  convenient,  in  lieu  of  a  special 
switch  adjustment  to  use  what  the  dealers  list  as  a  gain 
stroke  jaw,  although  it  might  more  properly  be  called 
a  "loose  stroke  jaw."  This  is  shown  in  Fig.  61.  Its 
action  is  the  same  as  that  of  a  special  switch  adjust- 

119 


120 


EAILWAY  SIGNALING 


ment.  It  may  either  be  attached  to  the  arm  of  the 
crank  which  throws  the  derail,  or  to  the  derail  itself, 
with  a  facing  point  lock,  or  to  the  arm  of  the  escape- 


HTBDBnflUUU 


Fig.  59. 

ment  crank,  or  to  the  derail  itself  with  a  switch  and 
lock  movement. 

With  the  Wharton  tvpe  of  derail,  a  special  switch 
adjustment  may  be  used. 

With  the  split  point  and  Wharton  types,  one  point 
lug  is  bolted  to  the  point,  and  a  lock  rod  shorter  than 
that  used  where  attached  to  the  middle  of  the  front 
rod,  is  connected  thereto. 

With  the  solid  type,  a  lug  to  which  the  lock  rod  may 
be  attached,  is  usually  made  a  part  of  the  derail. 

Fig.  6 1  shows  a  sectional  view  of  each  of  the  three 
types  already  illustrated,  with  gain  stroke  jaw  or 
special  adjustment  attached  to  each. 

Torpedo  machines  are  sometimes  used  in  lieu  of  de- 
rails, and  sometimes  as  an  adjunct  thereto.  These  de- 
vices are  arranged  so  that  when  the  lever  by  which  they 


IN  THEORY  AND  PRACTICE. 


121 


Fig.  60. 


122 


RAILWAY  SIGNALING 


are  operated  in  the  machine  is  set  normal  a  movable 
arm  carrying  a  detonating  torpedo  pushes  the  torpedo 
on  top  of  the  rail,  where  it  explodes  as  soon  as  a  wheel 
passes  over  it,  warning  an  engineman  of  danger  ahead. 
Where  used  they  should  be  placed  at  the  distant  sig- 
nal, so  that  an  engineman  will  have  time  to  stop  his 
train  before  over-running  the  home  signal,  if  his  en- 
gine should  explode  one.  As  an  adjunct  to  derails  in 
particularly  dangerous  places,  their  use  may  be  of 
value.  As  a  substitute,  however,  it  is  not  be  recom- 
mended, and  is  generally  forbidden  by  State  Authori- 


Fig.  61. 

ties.  As  the  magazines  of  these  devices  carry  only  a 
limited  number  of  torpedoes  they  require  constant 
attention  and  recharging. 

Interlocking  plants  are  frequently  used  to  protect 
the  approach  to  drawbridges,  so  that,  in  case  the  draw 
is  open  to  allow  for  the  passage  of  a  vessel,  trains  will 
be  thrown  from  the  track  by  a  derail,  or  diverted  to 
some  track  which  does  not  lead  onto  the  bridge,  to 
prevent  their  running  into  the  open  draw.  Several  ac- 
cidents entailing  appalling  loss  of  life  having  happened 
through  lack  of  proper  interlocking. 


IN  THEORY  AND  PRACTICE.  123 

As  a  general  thing  the  interlocking  machine  is  placed 
on  the  draw  itself,  although  sometimes  on  one  shore 
or  the  other;  in  either  case  some  or  all  of  the  pipe 
lines  leading  to  the  derails  and  signals  must  be  car- 
ried across  the  bridge,  and  must  be  so  arranged  that 
that  portion  of  them  which  is  permanently  attached  to 
the  bridge  may  be  disconnected  from  that  portion 
which  is  permanently  placed  on  shore,  whenever  the 
draw  is  to  be  opened.  This  is  done  by  using  a  bridge 
coupler,  one  of  which  is  illustrated  in  Fig.  62. 

The  pipe  lines  which  are  to  go  off  the  draw  are  at- 
tached to  jaws  with  rectangular  slots  in  their  ends, 
shown  as  a  a'  a"  a"'.  These  slots  when  the  jaws  are 
down  pass  over  hooks  b  b'  b"  b"'  in  the  other  half  of 
the  coupler,  thus  connecting  the  two  portions  of  the 
pipe  lines. 

Another  pipe  line  shown  as  c  is  attached  to  the 
side  of  the  frame  of  the  coupler,  shown  as  d,  so  that 
when  the  lever  to  which  this  pipe  is  attached  is  re- 
versed, the  frame  carrying  with  it  the  slotted  jaws  will 
be  raised,  as  shown  in  the  side  view,  and  all  of  the 
pipes  detached  at  once  from  their  corresponding  ex- 
tensions. The  draw  may  then  be  opened  and  when  it 
is  returned  to  its  normal  position  the  coupler  may  be 
dropped  and  the  pipes  thus  connected  again. 

On  a  railroad  drawbridge  the  end  rails  are  often 
made  so  that  they  may  be  raised  before  the  bridge  is 
swung,  and  where  this  is  the  case  bridge  locks  are 
applied.  The  general  principle  on  which  these  operate 
is  exactly  that  of  a  facing  point  lock  and  no  further 
description  will  be  given  here. 

So  far,  as  before  stated,  I  have  endeavored  to  bring 
only  such  matter  into  the  description  as  was  necessary 
to  give  the  reader  a  general  idea  of  the  subject  There 
are,  nevertheless,  a  few  general  questions  which  had 
better  be  explained  before  leaving  this  part  of  our  sub- 
ject. : 


124 


RAILWAY  SIGNALING 


In  describing  jaws,  both  solid  and  screw,  pipe  lugs, 
etc.,  I  have  spoken  exclusively  of  those  with  tanged 
ends.  Each  of  these  parts  is  also  made  with  a  stub 
end,  so  that  it  may  be  welded  to  a  bar  of  iron  instead 
of  being  attached  to  a  pipe.  As  explained  earlier, 
where  any  considerable  amount  of  offset  has  to  be 
made  in  a  pipe  line,  a  bar  of  solid  iron  should  be  let 
into  it,  and  the  offset  made  in  that.  If  it  is  convenient 
to  weld  a  jaw  on  one  end,  a  stub  end  jaw  should  be 
used,  as  it  is  a  little  cheaper.  Some  signal  men  will 


Fig.  62. 

cut  the  tang  end  off  a  solid  jaw  and  throw  it  away  so 
as  to  get  a  stub  end  jaw,  which  is  wasteful,  and,  there- 
fore, bad  practice.  All  types  of  jaws  used  with  one 
inch  pipe  may  be  had  of  dealers,  with  their  ends  tanged 
to  fit  three-quarter  uich  pipe  which  is  used  for  signal 
up  and  down  rods,  and  correspondingly  the  small  jaws 
using  a  five-eighths  instead  of  a  seven-eighths  pin, 
used  for  up  and  down  rods,  may  be  had  with  ends 
tanged  for  one  inch  pipe.  The  pipe,  it  should  be  un- 
derstood, is  measured  by  its  inside  diameter. 


IN  THEORY  AND  PRACTICE.  125 

Links  may  be  had  with  solid  jaws  on  each  end,  or 
with  a  screw  jaw  on  one  end.  The  latter  will  be  found 
the  more  convenient. 

Besides  the  jaws  already  mentioned  there  is  a  wide 
jaw  and  a  double  jaw.  The  former  is  intended  to  fit 
on  over  an  ordinary  jaw,  with  one  pin  holding  both 
of  them  to  a  crank  arm,  for  instance,  where  the  pipe 
line  is  carried  on  past  the  crank.  Double  jaws  are  like 
two  ordinary  jaws,  with  the  jaw  ends  joined,  and  are 
used  for  the  same  purpose.  Each  is  shown  in  Fig.  63. 
They  are  not  used  a  great  deal,  most  signal  engin- 
eers preferring  to  let  a  lug  into  the  line  and  connect 
that  to  the  crank  arm  with  a  link. 


Fig.  63. 

Where  interlocking  pipes  are  carried  across  bridges, 
through  tunnels  or  on  elevated  structures,  lateral  space 
is  often  very  restricted.  Compensators,  both  straight 
arm  and  lazy  jack,  are  furnished,  which  are  built  so 
that  they  stand  vertically  and  take  up  very  little  width. 

Compensation  on  swing  drawbridges  is  a  vexatious 
problem.  The  draw  itself  being  made  of  iron  or  steel, 
expands  and  contracts.  If  the  machine  is  on  the  mid- 
dle of  the  draw,  as  it  generally  is,  the  pipe  lines  are 
held  fast  there,  and  as  this  is  the  pivot  of  the  draw, 
they,  together  with  the  draw  itself,  expand  or  con- 
tract toward  or  away  from  the  free  ends.  The  half  of 
the  bridge  coupler  which  is  on  shore  being  attached  to 
the  ground  or  the  bridge  abutment  remains  station- 
ary, and  if  the  half  which  is  on  the  draw  moves  with 
it,  a  very  moderate  change  in  temperature,  if  the  draw 
is  a  long  one,  will  cause  enough  movement  in  the  free 


126  RAILWAY  SIGNALING 

ends  of  the  draw  to  prevent  the  slotted  jaws  in  the 
coupler  from  engaging  the  hooks. 

The  only  satisfactory  solution  of  this  problem  I 
have  yet  found  is  to  lay  a  heavy  plank,  wi,de  enough 
to  carry  the  bridge  coupler  and  compensators,  the  en- 
tire length  of  the  draw,  to  whose  centre  it  should  be 
rigidly  fastened,  but  free  at  the  ends.  The  com- 
pensator and  bridge  couplers  should  be  bolted  to  this 
plank;  which,  of  course,  if  the  draw  is  at  all  a  long 
one,  is  made  by  splicing  several  shorter  planks  to- 
gether at  the  ends.  As  wood  does  not  expand  and 
contract  as  iron  and  steel  do,  this  fixes  the  coupler  in 
a  permanent  location  with  reference  to  its  other  half 
on  the  shore  side,  and  to  the  machine.  The  com- 
pensators take  up  the  expansion  and  contraction  of 
the  pipe  itself  just  as  if  the  whole  arrangement  was 
on  solid  ground.  The  long  plank  may  be  guided  and 
held  from  moving  sideways  by  iron  stirrups  attached 
to  the  bridge  itself  and  fitted  around  the  plank  loosely 
enough  to  allow  the  bridge  to  expand  and  contract 
without  pulling  on  the  plank. 

To  guard  against  unnecessary  damage  caused  by 
derailments  at  interlocking  plants,  which  may  occur 
especially  at  derails,  the  main  pipe  lines  should  be 
kept  some  little  distance  from  the  track. 

Where  there  is  room  the  nearest  pipe  should  not 
be  closer  than  four  feet  to  the  nearest  rail  where  the 
pipe  lines  parallel  a  track,  and  a  greater  distance  than 
this  is  desirable  if  the  topographical  conditions  per- 
mit. 

Care  should  always  be  taken  that  "cross  pipes," 
pipes  crossing  the  track,  are  supported  at  least  every 
seven  feet,  either  by  transverse  pipe  carriers,  or  by 
setting  foundations,  with  tops  and  ordinary  carriers, 
between  tracks  which  are  some  distance  apart.  Where 
two  parallel  tracks  are  fourteen  feet  apart,  center 
to  center,  which  is  a  very  common  distance,  and  eight 


IN  THEORY  AND  PRACTICE.  127 

feet  ties  are  used,  transverse  pipe  carriers  should 
be  placed  six  inches  from  each  end  of  the  two  ties 
between  which  the  pipes  pass  in  each  track.  With 
wider  centers  it  is  better  to  set  a  foundation  and 
ordinary  pipe  carriers  midway  between  the  tracks. 

Signal  engineers  cannot  be  too  rigid  in  insisting 
that  the  Maintenance  of  Way  Department  shall  pro- 
vide the  very  best  drainage  at  interlocking  plants. 
Water  standing  around  detector  bars  and  then  freez- 
ing will  soon  completely  tie  up  a  plant. 

Sometimes  in  very  close  quarters  around  yards  and 
large  stations,  it  is  necessary  to  place  the  plunger 
castings  for  facing  point  locks  between  the  rails  of 
a  track,  in  which  case  the  front  rod  does  duty  also 
as  a  lock  rod.  It  is  made  flat  and  the  holes  for  the 
plunger  are  drilled  in  it.  This  practice,  however, 
should  be  avoided  wherever  possible. 

On  new  fills  likely  to  settle  considerably,  or  to 
slide  out,  it  is  good  practice  as  a  temporary  expedient 
to  fasten  the  pipe  carriers,  and  even  the  cranks  and 
compensators,  to  the  ends  of  long  ties  placed  every 
seven  feet  for  the  pipe  carriers;  three  ties  together 
for  the  compensators,  and  two  for  the  cranks.  As 
soon  as  the  fill  is  well  settled,  however,  concrete  or 
cast  iron  foundations  should  be  put  in  and  the  ties 
dispensed  with. 

Compensators  should  be  set  in  the  position  they 
occupy  with  the  lever  in  mid  stroke,  after  which  the 
arms  should  be  spaced  in  accordance  with  the  tem- 
perature tables  which  have  been  recommended  by 
the  Railway  Signal  Association. 

Railroads  which  handle  large  quantities  of  pack- 
ing-house products  find  that  the  brine  which  is  con- 
stantly dripping  from  refrigerator  cars  is  very  de- 
structive to  pipe  lines.  Some  relief  from  this  may 
be  had  by  using  galvanized  pipe  for  cross  pipes. 
Some  signal  engineers  use  it  for  all  piping,  but 


128  RAILWAY  SIGNALING 

my  experience  has  not  led  me  to  believe  that  its 
use  in  main  pipe  lines  is  of  enough  advantage  to  justify 
the  additional  expense.  Where  black  pipe  is  used  the 
pipe  lines  should  be  kept  well  painted  with  good  min- 
eral or  graphite  paint. 

It  not  infrequently  occurs  that  pipe  lines  have  to 
be  carried  under  ground,  as  for  instance,  where  they 
cross  a  paved  street.  In  such  cases  the  one  inch 
signal  pipe  is  frequently  run  through  a  two  inch 
galvanized  pipe  with  a  stuffing  box  to  fit  the  one  inch 
pipe  screwed  on  each  end.  The  two  inch  pipe  is 
then  filled  with  some  non-freezable  oil. 

Wires  too  are  often  run  through  one-half  inch  gal- 
vanized pipe  filled  with  oil,  with  a  stuffing  box  to  fit 
the  wire  screwed  on  its  ends. 

If  a  turn  in  a  pipe  line  has  to  be  made  under 
ground,  cranks  fitted  into  cast  iron  water-tight  boxes 
bushed  to  take  a  two  inch  pipe  where  the  jaws  enter 
are  used.  These  boxes  are  filled  with  oil  as  well 
as  the  pipe. 

Even  with  the  best  construction  a  certain  amount 
of  friction  is  present  in  every  pipe  and  wire  line,  and 
this,  of  course,  increases  with  the  length  of  the  line, 
so  that  a  point  will  eventually  be  reached  at  which 
the  power  exerted  on  the  lever  by  the  leverman  will 
be  entirely  expended  in  overcoming  this  resistance. 
Besides  this  pins,  jaws  and  the  holes  in  crank  and 
compensator  arms  are  continually  wearing,  so  that 
no  line  can  be  considered  as  entirely  free  from  lost 
motion.  It  has,  therefore,  been  found  advisable  to 
limit  the  "reach"  of  a  mechanical  interlocking  plant. 
In  England  railroads  are  forbidden  by  law  to  operate 
facing  point  switches  further  away  from  the  machine 
than  two  hundred  yards,  six  hundred  feet,  or  trailing 
point  switches  further  than  three  hundred  yards,  or 
nine  hundred  feet. 

In  America  we  have  very  few  switches  which  are 


IN  THEORY  AND  PRACTICE.  129 

not  used  as  facing  points,  at  least  occasionally.  A 
few  railroads  with  very  heavy  traffic  and  four  or 
more  tracks,  rarely  reverse  the  current,  but  so  much 
of  our  mileage  is  single  track  and  so  many  of  our 
double  track  railroads  reverse  traffic  occasionally,  that 
I  believe  the  foregoing  statement  is  correct. 

It  is,  therefore,  well  for  American  signal  engineers 
to  keep  nearer  to  six  hundred  than  to  nine  hundred 
feet  as  the  maximum  distance  a  switch  should  be 
away  from  the  lever  that  operates  it.  I  have  found 
seven  hundred  feet  to  be  a  very  satisfactory  maximum, 
except  in  rare  cases  where  the  pipe  line  can  be  run 
out  without  any  turns.  Some  signal  engineers,  how- 
ever, will  go  much  further  than  this,  and  there  is  no 
general  rule  in  American  practice,  as  there  is  in 
British. 

In  the  opening  article  of  this  work  I  said  that  the 
conventional  signs  used  by  signal  draftsmen  would 
be  illustrated  and  explained  as  the  necessity  for  so 
doing  developed. 

Fig.  64  shows  a  track,  a  crossing,  an  interlocking 
tower,  two  switches  and  three  derails.  The  reader 
should  note  that  one  of  the  switches  is  shaded  in, 
while  the  other  is  not.  The  shading  is  the  conven- 
tional method  of  showing  that  the  switch  is  included 
in  the  interlocking.  The  unshaded  switch  is  not  op- 
erated from  the  interlocking  machine.  The  line  next 
the  rail  in  front  of  the  shaded  switch  represents  the 
detector  bar.  Detector  bars  are  also  shown  for  the 
three  derails.  The  numbers  in  the  circles  denote  the 
numbers  of  the  levers  in  the  interlocking  machine 
by  which  the  signal,  switch,  derail  or  lock  near  which 
the  circle  is  drawn  is  operated.  Derail  No.  4  is  a 
split  point  derail;  No.  7  is  a  Wharton,  and  the  derail 
with  the  line  from  No.  5  is  a  solid  derail.  The  lines 
connecting  this  last  derail  and  the  switch  with  the 
figure  5  denote  that  lever  five  throws  both  the  switch 


130  RAILWAY  SIGNALING 

and  the  derail  simultaneously;  lever  No.  6  also  locks 
them  both.  The  letters  F.  P.  L.  after  the  figure  6 
show  that  this  is  a  facing  point  lock.  The  letters 
S  and  L  at  Nos.  4  and  7  show  that  these  derails  are 
operated  by  switch  and  lock  movements.  The  straight 


<Z> 


SAL. 


>— r 

© 


Fig.  64. 


line  in  the  tower  represents  the  machine,  and  the  dot 
the  leverman.  This  shows  at  a  glance  which  way 
the  machine  is  to  be  set.  The  home,  distant  and 
dwarf  signals  shown  have  already  been  explained. 


CHAPTER  X. 

POWER  INTERLOCKING. 

Before  taking  up  the  subject  of  power  inter- 
locking, I  shall  state  a  few  more  electrical  prin- 
ciples, an  understanding  of  which  is  necessary  to 
a  thorough  comprehension  of  the  subject. 

As  before,  I  shall  state  these  merely  as  facts, 
and  shall  not  take  space  or  the  reader's  time  to  go 
into  an  explanation  which  more  properly  belongs 
to  a  treatise  on  electricity  and  magnetism. 

(1)  When   two   plates   which   form   an   electric 
couple  are  submerged  in  an  electrolyte  in  which 
they  do  not  touch  each  other,  so  as  to  form  an  elec- 
tric  cell,   as   already   described,   it  is  known   as  a 
primary  cell. 

(2)  A  gravity  cell  is  a  primary  cell  in  which 
the  electric   couple   is   a   copper  plate  and  a  zinc 
plate.    The  copper  plate  is  placed  at  the  bottom  of 
the  jar  and  the  zinc  plate,  often  shaped  into  a  ring, 
is  suspended  part  way  up  the  jar.    The  electrolyte 
is  a  solution  of  copper  sulphate,  better  known  per- 
haps by  its  trade  name  of  blue  vitriol. 

(3)  A  gravity  cell  must  be  so  placed  that  a  cur- 
rent is  flowing  through  and  from  it  the  greater  part 
of  the  time.     That  is,  it  must  be  used  on   work 
where  the  circuit  is  almost  always  closed  and  only 
broken  intermittently;  otherwise  a  chemical  action 
takes  place  in  the  electrolyte  which  destroys  the 
capacity  of  the  cell  to  generate  an  electric  current. 

(4)  A  gravity  cell  must  be  cleaned  and  refilled 

131 


132  RAILWAY  SIGNALING 

every  four  or  five  weeks  whether  it  is  being  drained 
fast  or  slowly,  and  it  may  be  worked  to  its  full  ca- 
pacity without  shortening  its  life. 

(5)  A  primary  cell  whose  electric  couple  is  cop- 
per oxide  and  zinc,  and  whose  electrolyte  is  a  so- 
lution of  caustic  soda  is  known  under  the  general 
head  of  a  Lalande  cell. 

There  are  many  of  these  on  the  market,  as  the 
Edison,  the  Schoenmehl,  the  BSCO,  the  Gordon, 
the  Banks,  etc.,  etc.,  differing  from  each  other  in  their 
mode  of  construction. 

(6)  Lalande   cells   do   not   lose   their   efficiency 
when  not  generating  current.     They  may  be  used, 
therefore,  on  open  circuit  work.   Each  cell,  however, 
has  a  limited  output.     This  output  may  be  taken 
away  slowly,  in  which  case  the  cell  will  last  a  long 
time,  or  it  may  be  exhausted  very  quickly. 

(7)  A  dynamo  or  electric  generator  is   a  ma- 
chine  which    when   its    movable    part   is    revolved 
rapidly  will  produce  an  electric  current  just  as  a 
battery  will. 

(8)  An  electric  motor  is  a  machine  much  like  a 
dynamo,  the  movable  part  of  which,  when  an  electric 
current  is  supplied  to  it,  will  revolve  and  may  be  made 
to  do  work  just  like  a  steam  engine. 

(9)  If  the  direction  of  the  motion  of  the  movable 
part  of  an  electric  motor  is  reversed  the  motor  becomes 
a  generator  and  produces  an  electric  current. 

While  running  as  a  motor,  too,  what  is  known  as 
the  counter  electro  motive  force  is  being  generated  by 
a  motor.  By  making  proper  connections,  an  electric 
current  may  be  produced  by  this  counter  electro  mo- 
tive force,  which  as  will  appear  presently,  may  be  used 
to  advantage. 

(10)  A  storage  cell  is  a  cell,  the  plates  of  which 
are  made  of  lead;  one  nearly  pure  and  the  other 
chemically    prepared    (peroxide    of    lead),    and    the 


IN  THEORY  AND  PEACT1CE.  133 

electrolyte  of  which  is  dilute  sulphuric  acid  (oil  of 
vitriol).  When  the  plates  are  submerged  in  the 
electrolyte  and  externally  connected  together,  no 
current  is  generated,  but  if  a  current  from  some 
other  source  is  fed  into  the  plates  they  will  retain 
it  and  send  it  forth  again  just  as  a  primary  cell 
does.  A  collection  of  storage  cells  is  called  a  stor- 
age battery  or  accumulator. 

(11)  If  a  dynamo  is  used  to  charge  a  storage 
battery  enough  electricity  can  be  stored  in  one  day 
to  last  several  days,  thereby  saving  the  expense  of 
operating  the  dynamo  more  than  a  small  portion 
of  the  time. 

(12)  Nobody  knows  in  which  direction  an  elec- 
tric current  flows,  but  for  the  sake  of  having  a  uni- 
form practice  it  is  assumed  that  with  primary  cells 
it  flows  from  the  copper  plate  along  the  connecting 
wire  or  conductor,  as  it  is  called,  to  the  zinc  plate. 
The  connection  of  the  conductor  to  the  copper  plate 
is  called  the  positive  pole,  and  the  connection  of  the 
conductor  to  the  zinc  plate  is  called  the  negative 
pole. 

In  a  storage  battery  when  it  is  charged,  the  posi- 
tive plate  is  formed  of  peroxide  of  lead,  while  the 
negative  plate  is  almost  pure  lead. 

The  chemical  action  which  takes  place  while  the 
battery  discharges,  alters  the  composition  of  the 
plates,  and  they  both  become  a  lead  compound  in 
which  sulphur  appears. 

As  the  battery  is  recharged  the  condition  of  the 
plates  again  changes  through  the  chemical  action 
in  the  cells,  until  they  become  again  as  at  the  start* 
peroxide  of  lead  for  the  positive  and  pure  or  nearly 
pure  lead  for  the  negative. 

(13)  Electric  currents  may    be    converted    into 
mechanical  power  by  means  of  electro  magnets  as 
already  explained,  and  some  currents  may  be  able 


134  RAILWAY  SIGNALING 

to  produce  more  mechanical  power  than  others,  just 
as  a  steam  engine  with  a  pressure  of  two  hundred 
pounds  per  square  inch  in  its  boiler  will  give  a  stronger 
pull  on  the  piston  rod,  with  the  same  sized  cylinder, 
than  if  it  had  a  pressure  of  only  seventy-five  or  one 
hundred  pounds  per  square  inch.  The  power  of  a 
battery  is  measured  in  volts.  It  is  immaterial  for  pres- 
ent purposes  that  the  reader  should  be  given  a  complete 
definition  of  the  volt.  Suffice  it  to  say  that  it  is  the 
unit  or  gauge  by  which  the  ability  to  produce  mechani- 
cal power  in  a  cell  is  measured,  just  as  we  measure 
the  power  of  steam  in  a  boiler  by  pounds  per  square 
inch. 

(14)  The  amount  of  current  that  flows  from  a 
cell  is  measured  in  amperes.    The  ampere  does  not 
depend  on  the  voltage  of  the  cell  any  more  than 
the  amount  of  steam  let  out  of  a  boiler  depends  on 
the  pressure  in  the  boiler.     We  may  have  a  boiler 
with  fifty  pounds  pressure  per  square   inch,  with  a 
large  pipe  leading  from  it  through  which  ten  cubic 
feet  of  steam  passes  in  a  second,  and  we  may  have 
a   boiler   with   a   steam   pressure   of  two   hundred 
pounds  per  square  inch  with  a  very  small  pipe  lead- 
ing from  it  through  which  only  five  cubic  feet  of 
steam  passes  in  a  second.     Just  so  we  may  have  a 
cell  with  an  electric  pressure  of  one  hundred  volts 
from  which  we  are  drawing  a  current  of  one-tenth 
of  an  ampere  per  minute,  or  we  may  have  a  cell  with 
an  electric  pressure  of  two  volts  from  which  we 
may  draw  a  current  of  one  ampere  a  minute. 

(15)  Storage   cells    and   Lalande    cells   can    give 
forth   a   certain   amount   of  current,   and   when   that 
is    gone    they    are     exhausted.     They     are     usually 
rated  by  "ampere  hours."     A  cell  of  one  hundred 
ampere  hours  is  designed  to  give  forth  a  current 
of  one  ampere  continuously  for  one  hundred  hours, 


IN  THEOSY  AND  PRACTICE.  135 

or  of  one  hundred  amperes  for  one  hour,  or  of  six 
thousand  amperes  for  one  minute. 

This  last  statement  is  more  theoretical  than 
actual.  In  all  cells  there  is  a  resistance  between 
the  two  plates  inside  the  cell  known  as  the  internal 
resistance  which  prevents  a  cell  from  being  ex- 
hausted instantaneously,  no  matter  how  little  resist- 
ance there  is  in  the  external  circuit. 

The  current  may  be  drawn  off  continuously  until 
the  cell  is  exhausted  or  it  may  be  drawn  off  inter- 
mittently so  that  the  cell  may  last  months  or  even 
years  before  it  is  completely  drained. 

(16)  Gravity  cells  do  not  give  forth  a  limited 
amount  of  current,  but,  as  before  stated,  they  have 
to  be  cleaned  and  refilled  about  once  a  month.  They 
can  be  worked  to  their  full  output  all  the  time,  if 
properly  cared  for  that  often. 

(17)  Some  substances  allow  electric  currents  to 
pass  through  them  more  easily  than  others.     Such 
materials  are  said  to  have  low  resistances.     Silver, 
copper  and  iron  have  low  resistances.     Glass  and 
rubber  have   high   resistances.     The   resistance  of 
any  conductor  is  proportional  to  its  length.     That 
is,  if  one  foot  of  silver  wire  offers  a  certain  amount 
of  resistance,  two  feet  of  the  same  wire  will  offer 
just  twice  as  much,  and  so  on.    Volume  for  volume 
silver   offers   much   less   resistance   than   iron,   yet 
several  miles  of  silver  wire  may  offer  more  resist- 
ance than  a  few  inches  of  an  iron  wire  of  the  same 
diameter.     The  larger  the  section  of  a  conductor 
the  less  resistance  it  will  offer  for  a  given  length. 

(18)  Where  a  small  amount  of  current  is  all 
that  is  required  to  do  the  work  desired,  it  should 
be  drawn  from  the  cell  by  a  conductor  offering  con- 
siderable resistance.    If  the  resistance  is  decreased, 
more  current,  measured  in  amperes,  will  flow.     A 
conductor  may  be  likened  to  a  pipe  opening  into  a 


136 


RAILWAY  SIGNALING 


steam  boiler,  and  the  resistance  of  the  conductor 
to  the  diameter  of  the  pipe.  A  pipe  of  large  diameter 
would  draw  off  a  large  quantity  of  steam  in  a  given 
time;  a  conductor  of  low  resistance  would  draw 
off  a  large  quantity  of  electric  current  in  a  given 
time;  a  pipe  of  small  diameter  would  draw  off  a 
small  quantity  of  steam  in  a  given  time;  a  con- 
ductor of  high  resistance  would  draw  off  a  small 
quantity  of  electric  current  in  a  given  time. 

This  question  of  resistance  seems  to  perplex  a 
good  many  people.  It  appears  in  two  ways  in  sig- 
nal practice. 

(i)  Where  it  is  necessary  to  send  current  some 
distance  through  a  line  wire,  it  must  be  started  with 
pressure  enough  to  deliver  the  necessary  amount 
of  current  to  do  the  work  needed  at  the  far  end. 


Fig.  65. 

(2)  Where  current  is  being  drawn  from  a  stor- 
age or  caustic  soda  cell  the  conductor  must  offer 
enough  resistance  to  keep  the  drain  on  the  cell  down 
to  the  lowest  point  at  which  enough  current  to  do 
the  work  will  be  delivered  in  order  not  to  use  up 
the  cell  unnecessarily  fast. 

Wires  are  attached  to  parts  of  the  machine  to 
the  battery,  or  to  each  other  by  binding  posts, 


IN  THEORY  AND  PRACTICE.  137 

which  are  screw  and  nut  or  wide-headed  screw  ar- 
rangements designed  for  this  purpose. 

Fig.  65  shows  three  typical  styles  of  binding 
posts.  The  first  may  be  used  to  attach  two  wires  to- 
gether, or  to  attach  a  single  wire  to  the  pole  of  a 
battery,  for  instance.  With  this  type  the  ends  of 
the  wires  are  bent  around  into  a  hook  or  ring  and 
are  passed  over  the  threaded  part  of  the  post,  after 
which  the  nut  and  jamb  nut  are  screwed  down,  so 
as  to  squeeze  the  wires  together  tight  enough  to 
insure  a  good  electrical  connection. 

The  second  may  be  used  for  the  same  purpose.  In 
it  the  ends  of  the  wire  or  wires  are  passed  through  a 
hole  in  the  post  and  are  held  in  place  by  tightening 
down  the  screw,  a  thread  for  which  is  cut  in  the 
post. 

The  third  is  a  type  used  where  a  connection  between 
two  wires  is  made  through  a  terminal  board.  The 
wires  are  fastened  to  either  side,  and  as  the  body 
of  the  binding  post  is  of  brass  or  some  other  low 
resistance  metal,  the  current  flows  from  one  wire 
to  the  other. 

Mechanical  interlocking  has  been  on  trial  for 
more  than  fifty  years  and  may  be  said  to  have 
reached  its  full  development.  As  time  goes  on 
minor  improvements  may  suggest  themselves,  but 
there  is  little  likelihood  of  any  radical  or  sweeping 
changes  being  made  in  the  method  of  constructing 
either  the  machines,  switch  movements  or  signals. 
The  fundamental  principle,  too,  that  the  power  used 
is  always  the  same — a  man's  strength — has  tended 
toward  the  adoption  of  a  very  uniform  practice  with 
regard  to  the  construction  of  the  apparatus. 

With  power  interlocking,  the  opposite  condition 
may  almost  be  said  to  be  the  case.  Some  types  to 
be  sure  have  been  more  or  less  well  known  for  over 
twenty  years,  but  hardly  a  month  passes  without 


138  EAILWAY  SIGNALING 

the  introduction  of  entirely  new  devices  or  improve- 
ments in  the  old. 

Anything,  therefore,  written  about  the  power  in- 
terlocking of  today  may  become  out  of  date  in  a 
very  few  years. 

There  are,  nevertheless,  some  general  features 
common  to  all  types,  which  appear  to  have  settled 
themselves  into  standard  practice  and  are  likely  to 
continue  to  appear  in  any  future  developments. 

The  use  of  compressed  air  as  a  source  of  latent 
power  came  to  the  knowledge  of  railroad  men  with 
the  introduction  of  the  air  brake,  and  as  early  as 
1883  the  Union  Switch  and  Signal  Company  had 
placed  its  electro  pneumatic  interlocking  on  the 
market.  This  was  followed  by  the  so-called  low 
pressure  pneumatic  furnished  by  the  Pneumatic 
Signal  Co.  Then  came  the  Taylor  Signal  Com- 
pany with  the  first  all  electric  interlocking  to  come 
into  general  use.  This  in  turn  was  soon  followed  by 
the  Union  Switch  and  Signal  Company's  all  elec- 
tric, The  Federal  Railway  Signal  Company's  all 
electric,  The  American  Railway  Signal  Company's  all 
electric,  and  others  which  have  not  yet  had  the  good 
fortune  or  the  age  to  get  beyond  the  stage  of  the 
prospectus. 

I  shall  now  give  a  brief  description  of  the  op- 
erating and  locking  devices  and  signals  used  with 
each  of  the  machines  mentioned,  and  shall  add  a 
few  words  about  the  machines  themselves  used  by 
the  Federal  and  American  railway  signal  companies, 
about  which  nothing  was  said  in  the  chapter  on 
locking. 


CHAPTER  XL 

ELECTRO-PNEUMATIC   INTERLOCKING. 

The  operating  power  used  with  the  electro  pneu- 
matic interlocking  is  compressed  air.  This  is 
pumped  by  an  air  compressor  operated  by  a  steam 
or  gasoline  engine  or  an  electric  motor,  into  a  large 
storage  tank  or  reservoir  from  which  it  is  fed  into 
mains,  usually  two-inch  galvanized  pipe,  and  led  in 
the  most  convenient  way  which  the  nature  of  the 
ground  will  permit  to  the  vicinity  of  the  switches, 
derails  and  signals,  which  the  plant  is  designed  to 
operate,  from  which  it  is  carried  in  pipes  tapped  into 
the  main,  to  the  actual  devices  by  which  these 
switches,  derails  or  signals  are  moved.  The  main 
pipe,  and  frequently  its  branches,  at  least  for  part 
of  their  length,  is  usually  buried  in  the  ground, 
and  for  preservative  reasons  is  often  encased  in 
a  wooden  cover  which  has  previously  been  treated 
with  a  wood  preserving  compound.  The  air  is  kept 
at  a  pressure  of  from  65  to  85  pounds  per 
square  inch,  and  as  such  pressures  tend  to  con- 
dense any  moisture  which  is  in  the  air  at  the  time 
it  is  sucked  into  the  cylinder  of  the  air  compressor, 
means  of  draining  the  pipes  are  supplied  at  frequent 
intervals.  Towers  for  all  power  interlocking  ma- 
chines are  much  the  same  as  those  for  mechanical 
machines.  It  is  not  necessary  with  an  electro  pneu- 
matic plant  that  the  air  compressor  should  be  at 
the  tower.  Very  frequently  it  is  placed  in  a  build- 

139 


140  EAILWAY  SIGNALING 

ing  some  distance  away,  such  as  a  machine  shop  or 
round  house,  where  an  engine  is  required  for  other 
purposes,  which  can  also  operate  the  air  com- 
pressor, or  where  compressed  air  is  being  stored 
for  shop  purposes,  which  by  using  a  larger  com- 
pressor can  also  be  used  for  the  interlocking  plant. 
There  is  nothing  which  corresponds  to  the  leadout 
of  a  mechanical  plant,  with  an  electro  pneumatic 
plant. 

Besides  the  air  compressor  an  electric  battery  is 
necessary.  This  is  usually  placed  in  the  basement 
of  the  tower.  It  is  sometimes  a  storage  battery  and 
sometimes  a  collection  of  primary  cells.  A  wire  is 
run  from  the  positive  pole  of  this  battery  and  is 
connected  to  a  binding  post  in  one  end  of  the  ma- 
chine, back  of  the  locking  bed.  The  machines  for 
this  type  of  interlocking  are  so  arranged  that  the 
locking  bed  and  other  parts  are  contained  in  a  case 
supported  on  cast  iron  legs  at  about  the  height  of 
an  ordinary  man's  waist. 

The  machines  are  made  in  two  ways,  known  as 
the  "vertical  roller"  and  "horizontal  roller"  type. 
With  the  vertical  roller  machine  the  locking  shaft 
is  geared  to  another  shaft  placed  vertically  in  the 
back  of  the  machine,  the  second  shaft  being  en- 
cased in  a  hard  rubber  roller.  When  the  locking 
shaft  is  caused  to  make  a  partial  revolution  by  the 
leverman's  moving  his  lever,  which,  as  before  ex- 
plained, is  really  a  crank,  the  gearing  causes  the 
roller  to  revolve  also.  With  the  horizontal  roller 
machine  the  hard  rubber  roller  is  slipped  over  the 
locking  shaft  itself  between  the  locking  bed  and  the 
indication  magnets.  As  a  matter  of  fact  the  lock- 
ing shaft  is  made  in  three  pieces,  to  the  first  of 
which  the  driver  to  operate  the  locking  bar  is  at- 
tached, the  second  is  encased  in  the  hard  rubber 
roller,  and  the  third  holds  the  indication  segments. 


IN  THEOEY  AND  PRACTICE.  141 

These  three  pieces  are  jointed  together  so  as  to 
form  one  shaft. 

A  hard  rubber  rectangular  plate,  with  two  sets 
of  shallow  parallel  grooves,  one  set  running  longi- 
tudinally and  the  second  at  right  angles  to  the 
first  cut  or  moulded  in  its  side,  is  set  up  vertically 
just  in  front  of  the  rollers  in  a  vertical  roller  ma- 
chine, or  is  laid  down  horizontally  just  under  the 
rollers  in  a  horizontal  roller  machine.  In  either 
case  the  longitudinal  shallow  grooves  are  laid  at 
right  angles  to  the  axis  of  the  rollers.  In  these 
grooves  are  laid  thin  strips  of  brass  or  bronze. 
Thin  strips  of  the  same  metal  bent  into  arcs  of  a 
circle  are  attached  to  the  circumference  of  the  hard 
rubber  roller  in  planes  either  vertical  or  horizontal, 


Fig.  66. 

as  the  case  may  be,  coincident  with  the  center  line 
of  the  brass  strips  in  the  rubber  plate.  Wherever 
one  of  the  strips  in  the  hard  rubber  plate  passes 
under  or  alongside  of  one  of  the  rollers  to  which 
one  of  these  arc  shaped  strips  is  attached,  the 
former  strip  is  cut  apart  and  the  two  ends  thus  formed 
are  bent  away  from  the  rubber  plate  so  as  to  stand  out 
therefrom  on  either  side  of  the  roller. 


142  RAILWAY  SIGNALING 

Fig.  66  shows  a  sectional  view  of  a  portion  of  a 
hard  rubber  plate,  showing  the  bronze  strip  attached 
to  its  face  cut  apart,  and  with  the  ends  bent  out  and 
sections  of  a  hard  rubber  roller  with  an  arc  shaped 
brass  strip  attached  to  it. 

It  should  be  noticed  that  in  the  position  shown 
one  end  of  the  strip  or  band  attached  to  the  roller 
touches  the  end  of  one  of  the  bent  out  brass  strips, 
but  does  not  touch  the  other.  If,  however,  the 
roller  is  revolved  the  strip  attached  to  it  will  move 
with  it  and  will  soon  come  in  contact  with  the  bent  out 
end  which  it  did  not  before  touch.  It  will  still,  how- 
ever, remain  in  contact  with  the  other  bent  out  end. 
Now  if  one  end  of  the  brass  strip  attached  to  the 
hard  rubber  plate  is  attached  to  one  end  of  a  wire, 
the  other  end  of  which  is  attached  to  a  binding  post 
to  which  a  second  wire  leading  from  the  positive 
pole  of  the  battery  is  also  attached,  we  have  made 
a  path  for  an  electric  current  from  the  battery  up 
to  the  bent  out  end  of  the  strip  near  the  roller,  but 
here  the  path  is  broken  until  the  roller  is  revolved. 
After  it  is  revolved  we  know  that  the  current  has 
a  path  across  the  roller  to  the  other  part  of  the 
strip  attached  to  the  hard  rubber  plate.  Whether 
there  is  a  path  for  it  further  than  that,  we  have  not 
yet  seen.  Suppose,  however,  we  attach  a  wire  to 
the  outside  end  of  this  second  part  of  the  strip,  at- 
tached to  the  hard  rubber  plate,  and  carry  this  wire 
out  to  a  switch  a  thousand  feet  away,  where  we 
attach  its  end  to  the  end  of  a  wire  which  is  wrapped 
around  a  core  to  form  an  electro  magnet.  Then  let 
us  take  some  more  wire,  fasten  it  to  the  other  end 
of  that  wire  which  forms  the  magnet  coil,  and  lead 
it  back  to  the  machine  where  we  attach  it  to  the 
negative  pole  of  the  battery  by  means  of  another 
binding  post. 

It  can  now  be  seen  that  we  have  a  continuous 


IN  THEORY  AND  PRACTICE.  143 

path  for  the  current  from  the  positive  pole  to  the 
binding  post,  from  the  binding  post  to  the  bent  up 
bronze  strip,  where  we  have  a  gap  made  by  the  hard 
rubber  roller.  If  the  roller  is  revolved  in  the  di- 
rection of  the  arrow,  however,  we  have  a  path 
across  it  along  the  other  bent  up  strip,  thence  along 
the  wire  to  the  magnet,  through  the  magnet  coil 
back  on  the  other  wire  to  the  negative  pole,  through 
the  negative  plate  and  electrolyte,  until  we  come 
back  to  where  we  started  a^  >the  positive  pole.  The 
circuit  is,  therefore,  roiiiplete,  and  the  electro  mag- 
net out  at  the  switch  is  energised  and  holds  up  its 
armature.  Now  what  do  we  want  that  armature 
to  do? 

At  the  switch  we  have  a  cylinder  with  a  movable 
piston  and  piston  rod,  the  latter  attached  to  the 
slide  bar  of  a  switch  and  lock  movement  similar 
to  that  already  described  for  mechanical  interlock- 
ing. In  the  end  of  the  cylinder  is  a  valve  and  the 
armature  of  the  electro  magnet  is  attached  to  that 
valve.  One  of  the  pipes  leading  from  the  main  which 
connects  directly  with  the  air  reservoir  is  con- 
nected with  one  side  of  the  valve,  the  other  side  of 
which  opens  into  one  end  of  the  cylinder.  When 
the  magnet  is  energised  and  its  armature  up,  the 
valve  is  open,  and  compressed  air  from  the  pipe 
rushes  in  to  the  cylinder,  pushing  the  piston  ahead 
of  it,  moving  the  slide  bar  of  the  switch  and  lock 
movement,  and  throwing  the  switch  just  exactly  as 
if  the  slide  bar  was  being  pulled  or  shoved  by  a 
pipe  line  attached  to  a  lever  on  which  a  man  was 
pulling  or  pushing. 

Now  we  have  the  switch  reversed,  but  we  want 
to  get  it  normal  again,  how  are  we  going  to  do  it? 
By  cutting  another  flat  strip  on  the  hard  rubber 
plate,  bending  its  ends  up  just  like  the  first  one,  at- 
taching another  arc  shaped  strip  to  the  roller,  but 


144  RAILWAY  SIGNALING 

so  that  when  the  lever  is  normal  it  will  connect 
both  the  bent  out  ends  and  when  it  is  reversed  the 
path  for  the  current  through  them  will  be  broken, 
leading  another  wire  from  the  brass  strip  out  to 
the  switch,  connecting  it  to  another  electro  magnet 
in  another  valve  and  back  to  the  negative  pole  of 
the  battery,  just  as  we  did  before.  This  second 
valve  is  arranged  to  let  the  air  in  at  the  other  end 
of  the  cylinder. 

Now  we  have  an  arrangement  by  which,  when 
the  lever  is  normal,  air  is  being  admitted  to  one 
end  of  the  cylinder,  and  when  it  is  reversed  to  the 
other  end,  and  I  will  say  in  advance  of  a  further  ex- 
planation that  the  valves  are  so  arranged  that  when 
air  is  admitted  at  one  end  of  the  cylinder  it  is  al- 
lowed to  escape  from  the  other  end,  so  we  see  how 
the  switch  may  be  moved  from  one  of  its  positions  to 
the  other  by  first  reversing  the  lever  and  then  set- 
ting it  normal  again. 

There  are  reasons  why  so  simple  an  arrangement 
as  that  described  would  not  work  very  satisfactorily 
or  reliably  in  actual  practice,  and  the  valve,  or 
rather  system  of  valves,  actually  used  is  a  much 
more  complicated  arrangement  than  that  described. 
Instead  of  two  electro  magnets  there  are  three, 
known  as  the  normal  magnet,  the  reverse  magnet 
and  the  lock  magnet.  There  is  a  separate  wire  lead- 
ing from  each  of  the  magnets  to  one  of  the  brass 
strips  on  the  hard  rubber  plate.  These  strips  are 
so  arranged  through  their  bent  up  ends  and  the  arc 
shaped  strips  on  the  roller  that  current  is  sent 
through  the  wire  leading  to  the  lock  magnet  as  soon 
as  the  lever  is  moved  even  a  trifle,  either  from  its 
normal  or  its  reversed  position.  The  action  of  the 
lock  magnet  when  energised  affects  the  valves  so 
that  the  other  movements  will  follow. 


IN  THEORY  AND  PRACTICE. 


145 


Fig.  67  shows  a  section  of  a  switch  operating 
cylinder,  the  three  magnets  and  valves,  in  which  M2 
is  the  reverse  magnet,  M1  is  the  lock  magnet,  and 
M8  is  the  normal  magnet.  When  M1  is  energised  it 


u. 


Fig.  67. 


attracts  its  armature  m1,  moving  the  small  shaft  to 
which  the  armature  is  attached  in  the  direction  of 
the  arrow,  and  compressing  the  coil  spring,  d.  Be- 
tween the  coil  spring  and  the  magnet  coil  it  will 
be  noticed  that  the  shaft  which  is  attached  to  m1 
is  enlarged  so  as  to  act  as  a  pin  valve.  When  the 


146  EAILWAY  SIGNALING 

lock  magnet  M1  is  de-energised,  this  valve  closes 
the  connection  between  the  small  air  chamber  g2 
and  the  outer  air  by  way  of  the  exhaust  port  x1, 
but  when  it  is  energised  this  valve  is  opened  and 
the  air  in  c2  which,  as  will  be  seen  presently,  is  com- 
pressed air,  is  free  to  escape  through  g2. 

The  heavy  black  line  shown  as  g8  represents  a 
small  piston  fitting  tightly  in  the  air  chamber  c2  and 
held  down  by  a  coil  spring  d1  shown  in  section  by 
the  black  dots.  When  the  compressed  air  which 
was  in  c2  escapes,  its  pressure  which  has  been 
acting  on  the  piston  g8,  in  the  same  direction  as 
the  spring,  is  removed,  but  the  pressure  of  the  com- 
pressed air  on  the  other  side  of  g3  acting  against 
the  coil  spring  still  remains.  This  pressure  is 
enough  to  overcome  the  resistance  of  the  spring 
and  to  shove  g3  back  toward  the  lock  magnet.  At 
the  center  of  the  side  of  g3,  nearest  the  switch  cyl- 
inder is  a  pin  shown  as  g1.  When  g3  is  borne 
down  by  the  coil  spring  the  pin  engages  a  slide 
valve  d2,  which  is  placed  between  the  ends  of  two 
piston  rods  (omitted  from  the  drawing  for  clearness 
of  illustration)  which  are  connected  to  two  small 
pistons  k.  When  magnet  M1  is  energised  and  the 
air  in  c2  is  allowed  to  escape  so  that  the  pressure 
of  the  air  under  g3  compresses  the  coil  spring,  the 
pin  g1  is  raised  out  of  engagement  with  d2,  leaving 
d2  free  to  move.  All  this,  of  course,  happens  in  a 
very  brief  interval  of  time,  but  by  the  time  it  has 
happened  the  leverman  has  reversed  his  lever  far 
enough  to  send  a  current  through  reverse  magnet 
M2  by  making  another  connection  on  the  roller  in 
the  machine.  The  action  of  this  magnet  is  much 
the  same  as  is  that  just  described  of  M1,  that  is,  its 
armature  is  attracted,  pushing  the  armature  shaft 
toward  the  large  cylinder  and  opening  a  valve  at 
h1.  It  does  something  more,  however,  and  also 


IN  THEORY  AND  PRACTICE.  147 

closes  a  valve  at  c8,  thereby  preventing  any  air  from 
escaping  through  exhaust  x2. 

The  opening  of  the  valve  h1  makes  a  connec- 
tion between  the  air  chamber  which  connects 
directly  to  the  main  air  pipe,  and  the  air  space  back 
of  piston  k.  This  allows  air  to  get  behind  k  and 
shoves  it  toward  the  left,  carrying  with  it  slide 
valve  d2. 

At  the  same  time  that  magnet  M2  is  energised, 
magnet  M3,  which  has  been  energised  until  then,  is 
de-energised.  Spring  1  forces  the  armature  shaft 
outward  and  a  connection  is  made  for  the  com- 
pressed air,  which  is  behind  piston  j2,  to  escape 
through  exhaust  port  x8,  thereby  removing  any  re- 
sistance to  the  movement  of  piston  k,  behind  which 
compressed  air  is  rushing  from  the  main  air  pipe. 

When  d2  has  reached  a  point  where  its  hollow 
lower  side  bridges  over  the  main  exhaust  port  f 
and  the  connection  to  the  main  cylinder  e1  the 
compressed  air  in  the  cylinder  is  free  to  escape 
through  the  main  exhaust  port  f.  At  the  same  time 
compressed  air  from  the  main  pipe  passes  behind  d2 
and  into  the  connection  to  the  main  cylinder,  there- 
by getting  behind  the  main  piston  and  shoving  it  to 
the  opposite  end  of  the  main  cylinder,  which  reverses 
the  switch.  The  leverman  has  now  reversed  his  lever 
far  enough  to  break  the  circuit  through  lock  mag- 
net M1,  which  becomes  de-energised.  Its  armature 
is  pushed  back  by  the  small  coil  spring,  thereby 
closing  the  connection  to  the  exhaust  port  x1. 
There  is  a  very  small  hole  through  the  end  of  piston 
g8  near  pin  g1,  through  which  the  compressed  air 
from  the  main  pipe  soon  fills  up  air  chamber  c2.  The 
pressure  of  this  air  joined  to  the  pressure  of  the 
coil  spring  forces  g3  toward  the  main  cylinder  and 
locks  slide  valve  d2  in  its  reversed  position.  The 
fact  that  this  hole  is  as  small  as  it  is — much  smaller 


148  RAILWAY  SIGNALING 

than  exhaust  port  x1,  or  the  connection  to  the  main 
air  pipe,  prevents  enough  air  from  escaping  through 
it  to  fill  up  c2  as  fast  as  the  air  from  c2  escapes 
through  x1  when  M1  is  first  energised. 

The  switches  operated  by  the  cylinders  of  electro- 
pneumatic  plants  are  fitted  with  front  and  lock  rods, 
detector  bars,  braces  and  tie  plates,  in  all  essential 
particulars  exactly  as  those  operated  by  a  mechani- 
cal plant  are  fitted  up,  and  the  switch  is  locked  by 
the  switch  and  lock  movement  in  exactly  the  same 
way. 


CHAPTER  XII. 

ELECTRO-PNEUMATIC     INTERLOCKING — CONTINUED. 

In  the  earlier  part  of  the  foregoing  description, 
where  I  explained  the  action  of  the  contact  strips 
attached  to  the  hard  rubber  plate  in  the  machine 
frame,  and  the  running  of  the  wires  from  the  ma- 
chine to  the  switch  movement,  I  omitted  for  the 
sake  of  clearness  a  few  points  that  I  shall  now 
take  up. 

In  the  first  place  I  spoke  of  the  bronze  strips  be- 
ing bent  up  to  make  contact  with  the  arc  shaped 
strips  or  bands  on  the  rollers.  Taken  literally  this 
is  not  the  exact  case.  The  strips  laid  flat  in  the 
grooves  of  the  plate  are  cut,  but  instead  of  bending 
the  ends  up  to  the  roller,  other  strips  bent  to  the 
required  shape  are  screwed  down  to  the  hard  rub- 
ber plate  on  top  of  the  flat  strips  tight  enough  to 
insure  a  good  electrical  connection,  and  as  will  ap- 
pear further  on  the  flat  strips,  all  except  two,  are 
laid  in  the  cross  grooves  instead  of  the  longitudinal 
ones. 

As  regards  the  wiring.  One  wire  is  led  out  to 
each  of  the  three  magnets,  but  there  is  only  one 
wire  returning  to  the  negative  pole.  It  is  a  fact 
which  seems  a  little  strange  at  first,  but  is  plain 
enough  on  reflection,  that  as  many  wires  may  be 
led  out  of  a  battery  from  one  pole  as  we  please, 
and  that  after  the  current  carried  by  each  of  them 
has  done  its  work,  they  may  all  be  connected  to 

' 


150  EAILWAT  SIGNALING 

one  wire  called  the  "common  return  wire,"  or  "com- 
mon" wire,  and  the  circuit  for  each  of  them  completed 
through  this  one  wire. 

The  wires  leading  out  to  the  magnets  are  called 
the  control  wires.  The  common  wire  should  be  a 
heavier  one  than  the  control  wires  so  as  to  offer  the 
minimum  of  resistance. 

Attached  to  one  end  of  the  switch  and  lock  move- 
ment is  a  small  oblong  cast  iron  box,  called  the  in- 
dication box,  raised  a  little  above  the  plane  of  the 
upper  slide  bar.  This  box  is  divided  longitudinally 
down  the  middle  into  two  equal  compartments  by 
a  strip  of  vulcanized  fibre,  which  is  a  material  hav- 
ing a  very  high  resistance,  and  is,  therefore,  a  good 
insulator. 

In  each  of  these  compartments  are  two  stiff  brass 
springs.  The  ends  of  these  springs  near  the  middle 
of  the  box,  taken  lengthwise,  are  fastened  to  mica 
or  fibre  plates,  which  lie  horizontally  across  the 
box,  by  binding  posts.  These  ends  are  not  allowed 
to  touch  each  other  and  hence  do  not  form  part  of 
an  electric  circuit.  The  other  ends  of  these  springs 
are  bent  downward.  Two  wires,  with  their  other 
ends  connected  to  the  positive  pole  of  the  battery 
in  the  tower,  are  attached  to  one  end  of  the  wires 
which  make  the  magnet  coils  of  the  indication  mag- 
nets in  the  back  part  of  the  machine.  Other  wires 
are  connected  to  the  other  ends  of  these  coil  wires 
and  from  there  are  led  out  to  the  binding  posts 
which  connect  with  the  brass  springs  in  opposite 
ends  of  the  indication  box,  but  in  the  same  com- 
partment. 

Other  wires  are  connected  to  the  binding  posts  in 
the  opposite  compartment  of  the  indication  box,  the 
other  ends  of  which  join  to  the  common  return  wire. 

This  explanation  is  given  to  show  the  reader  as 
clearly  as  possible  how  the  indication  circuit  is 


IN  TEEOET  AND  PRACTICE.  151 

made  through  the  indication  box.  In  actual  prac- 
tice as  is  explained  a  little  further  on  the  current 
goes  out  to  the  indication  box  on  the  lock  control 
wire,  and  returns  on  two  separate  wires  through  the 
magnets  to  the  common  wire. 

A  lug  is  attached  to  the  upper  slide  bar  in  such  a 
way  that  when  the  switch  and  lock  movement  is  in 
its  normal  position  the  top  of  this  lug,  which  is  of 
a  low  resistance  material  and  is  carefully  insulated 
from  the  slide  bar,  bears  against  the  ends  of  the  two 
springs  in  one  end  of  the  indication  box,  thus  com- 
pleting a  circuit  from  the  positive  pole  of  the  bat- 
tery through  one  of  the  indication  magnet  coils,  to 
one  spring  in  the  indication  box,  across  to  the  other 
spring  by  way  of  the  lug  on  the  top  of  the  slide 
bar  of  the  switch  and  lock  movement,  from  the  last 
named  spring  to  the  common  wire  and  along  it  to 
the  negative  pole  of  the  battery. 

When  the  switch  and  lock  movement  is  moved 
toward  the  reverse  position,  this  lug  soon  gets  be- 
yond the  bent  down  ends  of  the  springs  and  ceases 
to  touch  them.  The  circuit  is  then  broken.  Just 
before  the  switch  and  lock  movement  completes  its 
stroke,  however,  the  lug  touches  the  ends  of  the 
two  springs  in  the  other  end  of  the  indication  box, 
making  an  electrical  connection  between  them,  thus 
closing  the  circuit  through  the  other  indication 
magnet  in  the  machine.  Therefore,  whenever  the 
switch  and  lock  movement  is  at  the  full  end  of  its 
travel,  a  circuit  is  completed  through  one  indica- 
tion magnet  or  the  other.  It  is  not  advisable,  how- 
ever, to  leave  this  circuit  closed  all  the  time,  as  it 
serves  no  useful  purpose  to  do  so,  and  simply  draws 
current  from  the  battery  unnecessarily.  So  instead 
of  running  wires  direct  from  the  positive  pole ^  of 
the  battery  to  the  indication  magnets,  a  connection 
is  made  near  the  switch  between  the  positive  side 


152  EAILWA7  SIGNALING 

of  the  indication  box  and  the  lock  control  wire.  Two 
wires  are  then  run  from  the  negative  side  of  the  in- 
dication box,  one  to  each  indication  magnet,  and 
from  there  are  carried  by  contact  springs  across 
the  hard  rubber  roller,  which  is  moved  when  the 
lever  moves  in  practically  the  same  manner  in  which 
the  lock  circuits  and  normal  and  reverse  switch 
valve  circuits  are  carried  across,  but  are  then  con- 
nected by  the  common  wire  to  the  negative  pole  of 
the  battery.  This  will  be  explained  presently  after 
we  have  said  a  few  words  on  the  divisibility  of  elec- 
tric currents. 

There  is  another  difference,  also,  which  is  this: 
The  hard  rubber  roller  to  which  the  arc  shaped 
bands  which  complete  the  circuit  for  the  indication 
wires  are  attached,  is  not  a  part  of  the  same  hard 
rubber  roller  to  which  the  circuit  closing  bands 
which  connect  the  lock  and  valve  wires  are  at- 
tached. It  is  a  separate  roller,  encasing  the  same 
shaft,  but  so  arranged  that  it  does  not  commence 
to  move  until  the  lever  has  made  five-sixths  of  its 
stroke.  It  then  commences  to  move  and  soon  makes 
the  contact  by  which  the  circuit  through  the  indi- 
cation magnet  is  closed — either  the  reverse  or 
normal — according  to  whether  the  lever  is  being 
reversed  or  set  normal. 

When  the  indication  magnet  becomes  energised 
the  lever  is  free  to  complete  its  stroke  as  already  de- 
scribed in  an  earlier  chapter,  but  in  so  doing  it 
breaks  the  circuit  through  the  indication  magnet 
and  leaves  it  de-energised. 

The  cylinders  used  to  operate  high  signals  are 
different  from  those  used  to  operate  switches.  They 
are  attached  vertically  to  the  signal  poles  and  com- 
pressed air  is  admitted  to  one  end  only,  so  as  to 
shove  down  on  the  piston  which  is  connected  to 
the  up  and  down  rod  by  a  straight  arm  compensa- 


IN  THEORY  AND  PRACTICE.  153 

tor  which  reverses  the  motion  so  that  an  upward 
thrust  is  transmitted  to  the  up  and  down  rod.  The 
force  of  gravity  is  depended  on  to  restore  the  sig- 
nal to  the  normal  position. 

There  is  but  one  indication  given  by  a  signal,  and 
this  is  from  its  normal  position.  When  the  blade 
goes  to  clear,  it  does  not  indicate.  The  reason  for 
this  is  that  if  a  signal  should  stick  in  the  normal 
position  after  the  leverman  had  reversed  the  lever 
no  great  harm  could  be  done  by  his  then  being  able 
to  reverse  other  levers  which  the  first  lever  would 
have  unlocked.  The  mechanism  of  these  signals  is 
very  reliable  also,  and  the  chances  of  their  sticking 
at  normal  are  remote. 

It  is  the  general  practice  to  place  the  signal  cyl- 
inders at  the  base  of  the  pole  and  to  run  the  up 
and  down  rods  inside  of  the  pole. 

Recently  some  electro  pneumatic  signals  have 
been  manufactured  which  have  the  cylinders  on  the 
top  of  the  pole.  This  is  a  mode  of  construction 
which,  as  will  be  seen  later,  appears  in  several  types 
of  electric  signals. 

The  cylinders  of  electro  pneumatic  dwarf  signals 
are  in  the  base  of  the  pole,  and  are  so  arranged  that 
they  shove  up  only  on  the  up  and  down  rod,  against 
the  action  of  a  strong  coil  spring.  When  the  air  is 
released  this  spring  acts  as  a  counter  weight  and 
restores  the  signal  to  normal.  In  the  case  of  the 
dwarf  signal  the  piston  remains  stationary,  while 
the  cylinder  itself  to  which  the  up  and  down  rod  is 
attached  moves  upward  by  the  reaction  of  the  com- 
pressed air  against  the  fixed  piston. 

Instead  of  the  indication  box  as  used  with  switch 
movements,  the  indication  circuit  is  closed,  on  the 
dwarf  signals  by  a  brass  plate  attached  to  the 
side  of  the  cylinder,  which,  when  the  signal  is  nor- 
mal and  the  cylinder  down,  presses  against  a  stiff 


154  -RAILWAY  SIGNALING 

vertical  spring  in  the  bottom  of  the  dwarf  signal 
case.  The  wire  forming  the  indication  circuit  is 
attached  to  this  spring  by  a  binding  post,  where  it 
is  cut  off  and  the  severed  end  attached  by  another 
binding  post  to  the  brass  plate,  so  that  when  the 
cylinder  is  up  and  the  signal  clear  the  indica- 
tion circuit  is  broken,  but  when  the  cylinder  is 
down  and  the  signal  normal,  the  indication  circuit 
is  closed. 

With  high  signals  a  circuit  controller  made  of 
two  springs  which  do  not  touch  each  other  between 
which  a  low  resistance  slide  is  forced  when  the  sig- 
nal is  normal  by  the  movement  of  the  piston,  is 
bolted  to  the  side  of  the  cylinder.  The  cylinder 
air  valve  with  its  electro  magnet  and  circuit  con- 
troller is  protected  by  a  neat  cast  iron  casing, 
which  is  fastened  to  the  signal  pole  or  ladder  by  a 
chain  so  that  it  cannot  be  carried  away  and  the 
mechanism  left  exposed. 

With  both  high  and  dwarf  signals  the  circuit  con- 
trollers should  always  be  insulated  from  the  poles. 

It  should  be  noted  that  there  are  no  balance  lev- 
ers, "L"  cranks  or  counter  weights  with  these  sig- 
nals. The  arm  plate  castings  are  made  very  heavy 
on  the  side  opposite  the  blade,  and  the  up  and  down 
rods  are  of  solid  iron  instead  of  pipe,  which  gives 
them  considerable  weight  also,  so  that  counter 
weights  as  they  appear  with  mechanical  signals 
are  dispensed  with. 

As  stated  in  a  previous  chapter  on  locking,  a 
switch  and  signal  lever  are  differently  arranged 
in  an  electro  pneumatic  machine.  We  will  now 
consider  the  points  of  difference. 

In  the  first  place  signal  levers  are  always  ar- 
ranged in  the  machine  so  that  they  extend  below 
the  horizontal  line  through  the  centers  of  the  lock- 
ing shafts,  while  switch  levers  are  arranged  to  ex- 


IN  THEOEY  AND  PRACTICE.  155 

tend  above  that  line.  Incidentally  it  may  be  said 
that  switch  levers  are  always  given  odd  numbers, 
while  signal  levers  are  always  given  even  numbers. 

In  their  normal  position  signal  levers  are  verti- 
cal. 

In  their  normal  position  switch  levers  are  in- 
clined to  the  left  of  a  person  facing  the  front  of 
the  machine,  at  an  angle  of  30  degrees  from  the 
vertical.  •  *  j 

When  reversed  signal  levers  may  be  thrown 
either  to  the  right  or  the  left  of  the  vertical,  30  de- 
grees to  either  side. 

When  reversed  switch  levers  can  be  moved  only 
to  the  right  of  the  vertical,  also  30  degrees,  making 
their  full  stroke  60  degrees. 

From  the  above  it  will  be  seen  that  signal  levers 
have  two  reverse  and  one  normal  positions,  and 
can,  therefore,  be  used  to  clear  two  signals.  The 
principal  of  having  switches  select  their  signals  is 
also  used  wherever  possible.  This  affects  a  great 
saving  in  the  number  of  levers  necessary  to  operate 
the  signals  at  a  given  plant. 

The  method  of  closing  the  indication  circuit,  or 
as  it  is  called  when  a  signal  lever  is  referred  to, 
the  lock  circuit,  is  also  different.  Both  switch  and 
signal  levers  are  held  in  their  normal  or  reversed 
position  by  small  latches  which  are  pressed  down 
by  springs  and  are  intended  to  prevent  levers  be- 
ing unintentionally  moved  by  a  person  brushing 
along  the  front  of  the  machine. 

When  the  leverman  takes  hold  of  the  small  hard 
rubber  knob  which  serves  as  a  hand  hold,  he  has 
to  press  it  away  from  the  fulcrum  o*  the  lever  in 
order  to  unlatch  the  lever,  so  that  he  can  move  it. 
As  the  signal  lever  does  not  have  to  get  an  indica- 
tion, or  be  unlocked,  in  a  movement  from  normal 
to  reverse,  as  a  switch  lever  does,  it  has  only  one 


156  SAILWAT  SIGNALING 

magnet  to  energise  and  consequently  one  circuit 
to  close. 

The  latch  in  the  handle  is  made  to  work  a  cir- 
cuit controller  near  the  front  of  the  machine  for 
this  purpose.  This  saves  having  the  extra  hard 
rubber  roller  for  a  signal  lever  that  is  required 
for  a  switch  lever  with  its  contact  strips  and  other 
attachments. 

As  with  other  mechanical  apparatus,  it  is  the  ob- 
ject of  the  designers  of  interlocking  machinery  not 
to  use  more  material  in  its  construction  than  is  ab- 
solutely necessary  to  accomplish  the  work  for  which 
it  is  intended. 

It  is  another  fact  about  electric  currents,  that  in 
case  a  conductor  is  divided,  the  current  will  also 
divide  itself,  and  follow  each  different  part  of  the 
conductor,  provided  they  all  offer  an  unbroken  path 
for  its  return  to  its  source.  The  question  of  resist- 
ance has  to  be  taken  into  consideration  in  some 
cases  where  this  principle  is  applied,  but  just  now 
we  will  omit  reference  to  that  part  of  the  subject. 

This  quality  of  divisibility  of  an  electric  current 
is  made  use  of  in  constructing  electro  pneumatic 
interlocking  machines,  and  in  a  great  many  other 
ways,  as  well,  in  signal  work. 

Heretofore  I  have  considered  the  action  of  one 
lever  taken  singly  with  regard  to  its  action  in  op- 
erating a  switch  or  signal  but  where  there  are  many 
levers  together  in  an  interlocking  machine,  the 
question  of  economizing  space  and  material  comes 
to  the  fore. 

From  the  principle  of  the  divisibility  of  the  cur- 
rent,, it  is  easily  seen  that  it  is  unnecessary  to  have 
more  than  one  wire  attached  to  the  positive  pole  of 
the  battery,  and  if  this  wire  can  be  brought  up  to 
the  hard  rubber  plate  in  the  machine,  which  we 
will  hereafter  call  the  contact  plate  and  there  ar- 


IN  THEORY  AND  PRACTICE. 


157 


ranged  so  that  each  of  the  bent  up  brass  strips  will 
act  as  a  separate  branch  of  this  conductor,  we  may 
feed  a  great  number  of  circuits  from  it  and  save 
a  great  many  separate  wires  and  their  connections 
between  the  brass  contact  strips  and  the  battery. 

Fig.  68  shows  a  view  of  a  contact  plate  with  hard 
rubber  roller  crossing  it.     It  will  be  noted  that  two 


'indication  Box. 


Fig.  68. 


of  the  strips,  and  only  two,  extend  to  the  left  side  of 
the  contact  plate.  To  one  of  these  the  feed  wire  from 
the  battery  is  attached  by  a  suitable  binding  post. 

The  other  is  attached  to  the  common  wire  near 
the  negative  pole  of  the  battery,  and  is  used  as  a 
path  for  the  return  current  which  operates  the  in- 
dication magnets  back  to  the  battery. 

The  lever  represented  in  the  figure  is  a  switch  lever 
and  has  five  contact  strips  raised  on  each  side  of  it, 


158  SAILWAY  SIGNALING 

and  five  arc  shaped  bands  attached  to  it.  The  ends 
of  three  of  them  are  connected  to  another  strip 
running  at  right  angles  to  the  strip  to  which  the 
feed  wire  is  connected  and  parallel  to  the  roller. 
This  transverse  strip  not  only  connects  each  of  the 
three  contact  strips  on  one  side  of  the  roller  to- 
gether, but  also  joins  them  to  the  long  feed  strip 
sometimes  called  the  battery  strip.  The  current, 
therefore,  may  come  from  the  battery  to  the  feed 
strip,  along  the  transverse  strip  to  the  first  contact 
strip,  and  if  the  circuit  is  closed  through  that,  part 
of  the  current  will  be  drawn  off  there.  If  another 
or  all  of  the  other  contact  strips  should  be  part  of 
closed  circuits,  each  would  draw  off  its  share  of 
current  from  the  battery. 

The  two  other  contact  strips  on  the  same  side 
of  the  roller  are  also  joined  together  by  another 
transverse  band,  which  connects  them  to  the  second 
longitudinal  strip.  These  are  the  contacts  for  the 
indication  magnets.  The  second  long  strip  is  con- 
nected to  the  common  wire. 

The  contact  strips  on  the  other  side  of  the  hard 
rubber  roller,  it  will  be  noticed,  are  not  connected 
together,  or  to  the  feed  strip.  These  are  joined 
by  screws  through  the  contact  plate  to  binding  posts 
on  its  lower  side,  from  which  wires  are  run  to  sep- 
arate binding  posts  on  the  terminal  board  already 
mentioned,  which  is  attached  to  the  back  of  the  ma- 
chine, so  that  external  wires  leading  to  the  lock 
magnet,  the  normal  and  reverse  valve  magnets,  and 
the  indication  box  may  be  joined  to  them  by  being 
attached  to  the  same  binding  post,  on  the  other 
side  of  the  terminal  board. 

As  before  stated  it  is  neither  necessary  nor  ad- 
visable to  keep  the  indication  magnets  on  a  switch 
lever  energised  longer  than  just  time  enough  to  re- 


IN  THEORY  AND  PEACTICE.  159 

lease  the  lever  so  that  it  may  complete  its  stroke, 
so  a  use  of  the  principle  of  divisibility  of  current  is 
made  there. 

The  contact  strips  and  bronze  contact  bands  on 
a  switch  lever  by  which  current  is  sent  through  the 
lock  magnet  are  so  arranged  that  the  lock  magnet 
is  not  energised  except  when  the  lever  is  part  way 
over,  either  toward  its  full  reverse  or  full  normal 
position,  and  it  is  while  the  lever  is  in  this  position 
that  the  indication  circuits  need  to  be  closed.  The 
two  springs  in  the  indication  box  which  are  con- 
nected to  the  positive  pole  of  the  battery  are,  there- 
fore, joined  together  in  the  indication  box  by  a 
small  brass  strip  held  down  by  their  binding  posts, 
and  a  short  wire  is  run  from  one  or  both  of  these 
binding  posts  in  the  indication  box  to  connect  with 
the  lock  magnet  wire  from  the  machine.  The  cur- 
rent which  comes  out  from  the  positive  pole  of  the 
battery  on  the  lock  magnet  wire  divides  near  the 
switch,  therefore,  and  whenever  the  switch  is  in 
either  full  position  so  as  to  close  one  or  the  other 
of  the  indication  circuits  part  of  this  current  crosses 
through  the  indication  box. 

In  the  side  of  the  indication  box  opposite  that 
to  which  the  short  wire  connecting  to  the  lock 
magnet  wire  connects,  the  springs  are  not  joined, 
and  by  their  binding  posts  are  connected  independ- 
ently to  the  normal  and  reverse  indication  magnet 
by  wires  running  back  to  the  machine.  The  other 
sides  of  the  indication  magnet  coils  are  connected 
to  the  common  return  wire  and  by  that  the  current 
finds  its  way  back  to  the  negative  pole  of  the  bat- 
tery. Thus  it  may  be  seen  that  the  current  energises 
the  indication  magnets  as  it  returns  from  the  switch, 
instead  of  as  it  goes  out  to  the  switch;  any  break 
in  the  lock  magnet  circuit  also  breaks  the  indica- 
tion circuit  so  that  when  the  lever  is  in  its  full  nor- 


160  RAILWAY  SIGNALING 

mal  or  reversed  position  which  can  only  be  after 
the  switch  has  gone  to  its  full  normal  or  reversed 
position  and  has  closed  the  circuit  through  the  in- 
dication box,  the  indication  circuit  is  broken  at  the 
hard  rubber  roller  because  the  lock  circuit  is  also 
broken  there.  This  saves  unnecessary  battery  con- 
sumption. 

It  is  sometimes  convenient  to  operate  both  ends 
of  a  crossover  with  one  lever,  both  in  mechanical 
and  electro  pneumatic  work.  Where  this  is  done 
with  the  electro  pneumatic,  separate  cylinders  and 
switch  and  lock  movements  are  put  in  at  each 
switch,  but  the  lock  wire,  the  normal  and  the  re- 
verse valve  wires  are  run  through  the  correspond- 
ing magnets  at  each  switch  before  being  connected 
with  the  common.  In  this  way,  every  time  that 
one  of  them  is  energised  the  other  must  be  also, 
being  on  the  same  circuit,  so  that  the  switches  per- 
form exactly  alike.  In  the  same  way  both  indica- 
tion circuits  are  run  through  both  indication  boxes, 
and  unless,  therefore,  both  switches  are  over  and 
locked,  the  indication  magnet  will  not  be  energised 
and  the  lever  will  be  prevented  from  making  its 
full  stroke.  Movable  point  frogs  are  thrown  by 
tandem  switch  and  lock  movements. 

Besides  the  type  of  switch  and  lock  movement 
already  described,  one  using  a  motion  plate  instead 
of  an  escapement  crank,  is  sometimes  used,  and  in 
some  cases  the  lock,  normal  and  reverse  control 
magnets  and  their  valves,  are  fitted  to  the  end  of 
the  switch  cylinder  instead  of  on  its  side.  These 
are  mere  details  of  construction  and  have  no  bear- 
ing on  the  principle  involved  in  this  apparatus. 

It  is  a  general  custom  to  turn  out  electro  pneu- 
matic machines  with  what  is  known  as  a  track 
model  fastened  to  the  back  of  the  machine.  This 
track  model  consists  of  an  upright  solid  wooden 


IN  THEOEY  AND  PRACTICE.  161 

frame  on  which  a  plan  of  the  tracks,  with  the 
switches  operated  by  the  machine,  is  shown  by  rec- 
tangular brass  rods;  miniature  signals  are  also 
shown.  The  switches  and  signals  are  made  movable 
and  are  mechanically  attached  to  the  levers  which 
operate  them,  by  small  cranks  and  rods,  so  that  the 
leverman  has  a  moving  model  of  the  switches  and 
signals  controlled  by  the  machine  before  him  as  he 
operates  the  machine. 

It  may  be  that  years  ago  when  expert  levermen 
were  scarce,  this  track  model  served  some  useful 
purpose,  but  other  makes  of  machines  are  now  suc- 
cessfully operated  without  it.  Its  cost  is  consid- 
erable and  as  trained  levermen  may  always  be  had, 
it  might  as  well  be  dispensed  with. 

As  will  be  noted  later,  what  is  known  as  a  manip- 
ulation chart,  which  also  comprises  a  track  and  sig- 
nal plan,  should  be  hung  up  in  every  tower. 

As  before  stated,  the  air  pipes  of  an  electro  pneu- 
matic plant  are  provided  with  drainage.  The  air, 
too,  after  leaving  the  compressor  is  run  through 
cooling  coils  and  such  moisture  as  is  thereby  con- 
densed is  held  in  the  main  reservoir  where  it  can 
be  drained  off  whenever  necessary  by  suitable  stop 
cocks.  At  each  switch  or  signal  movement  an 
c.;:xiliary  reservoir  is  provided,  into  which  the  air 
from  the  main  pipe  is  emptied,  and  from  which  it 
is  drawn  off  to  the  switch  and  signal  cylinders. 
These  auxiliary  reservoirs  catch  any  moisture  which 
is  not  deposited  in  the  main  reservoir,  and  it  is  from 
them  that  the  drainage  is  made  by  stop  or  blow  off 
cocks. 

Gate  valves  are  also  cut  into  the  main  air  pipe 
at  frequent  intervals  so  that  in  case  a  leak  should 
occur  in  this  pipe  some  distance  away  from  the 
tower,  air  may  be  shut  off  from  the  broken  part, 
and  all  switches  and  signals  between  the  point  where 


162  EAILWAY  SIGNALING 

a  gate  valve  is  closed  and  the  machine  kept  work- 
ing while  repairs  are  being  made.  Each  of  the 
small  pipes  leading  to  a  switch  or  signal  cylinder, 
too,  is  provided  with  a  stop  cock,  so  that  that  par- 
ticular switch  or  signal  may  be  cut  out,  in  case  of 
a  leak,  without  necessitating  the  shutting  down  of 
the  entire  plant. 

The  connections  from  the  auxiliary  reservoirs  to 
the  operating  switch  cylinders  are  usually  flexible, 
steel  covered  hose  being  generally  used.  Trains 
passing  over  switches  jar  the  connections  a  good 
deal,  and  by  having  them  flexible  this  jar  is  not 
transmitted  to  the  connection  with  the  auxiliary 
reservoir. 

With  the  signal  cylinders  this  does  not  matter 
so  much,  as  the  signals  are  not  moved  by  the  deflec- 
tion of  the  rails  in  the  track. 

The  wire  used  is  copper,  covered  with  a  coating 
of  a  compound  of  india  rubber  from  3/64  in.  to 
5/64  in.  thick  over  which  one  or  two  strands  of  braid 
are  wound.  Cables  are  often  used  for  switch  and 
signal  movements.  It  is  as  well  to  have  two  or 
three  extra  wires  in  the  cables,  so  that  in  case  one 
breaks  inside,  the  circuit  of  which  it  forms  a  part 
may  be  transferred  to  a  spare  wire. 

The  control  wires  are  usually  No.  12  or  No.  14 
Brown  and  Sharpe  gauge  and  the  common  No.  8 
or  9. 

The  wires  or  cable  are  carried  in  a  conduit  usually 
called  trunking.  Where  the  circumstances  do  not 
require  that  this  should  be  very  large  it  is  often 
grooved  out  of  two,  three  or  four  inch  plank,  with 
a  flat  board  called  the  cap  to  close  in  the  fourth  side 
or  top.  Large  trunking  is  generally  made  of  four 
planks,  which  should  be  dressed  to  exact  size,  if  a 
good  looking  job  is  desired,  nailed  together  to  form 


IN  THEORY  AND  PRACTICE.  163 

a  box.  The  object  of  trunking  is  to  protect  the 
delicate  wires  from  mechanical  injury. 

The  best  practice  is  to  keep  the  trunking  above 
ground.  Where  this  is  done,  it  should  be  nailed 
to  a  row  of  stakes  set  8  feet  apart.  Three  inch 
by  4  inch  oak  stakes,  4  feet  long,  the  same  as 
those  used  for  wire  lines  at  mechanical  interlock- 
ing plants  are  as  good  as  anything,  and  look  neat. 
Some  signal  engineers  prefer  to  use  cedar  fence 
posts,  sawed  in  two,  and  others  use  stakes  made 
of  old  boiler  flues  or  old  pipe. 

Wooden  trunking  is  one  of  the  most  unsatisfac- 
tory classes  of  material  a  signal  engineer  has  to 
use.  Frequent  attempts  have  been  made  to  intro- 
duce an  underground  conduit  of  some  sort,  but  the 
ability,  which  overground  trunking  affords,  to  get 
at  the  wires  at  any  time  without  much  labor,  is  an 
advantage. 

Care  should  be  taken  in  nailing  down  the  capping 
not  to  let  the  nails  dodge  and  break  or  cut  through 
the  insulation  of  wires  or  cable  inside  the  trunking. 

Where  wires  have  to  be  led  away  from  the  main 
trunking  line,  it  will  be  found  very  convenient  to 
use  a  junction  box.  This  is  a  box  let  into  the  trunk- 
ing, inside  of  which  is  a  terminal  board  usually  of 
slate  or  porcelain,  or  some  high  resistance  material, 
into  which  several  binding  posts  are  screwed.  The 
wires  in  the  main  trunking  have  their  ends  at- 
tached to  the  binding  posts,  and  the  wires  which 
lead  from  them  are  attached  to  the  same  binding 
posts. 

The  reader  may  have  noticed  that  in  every  case 
where  connections  for  circuits  are  made  and  broken 
intermittently,  it  is  by  a  spring  rubbing  against  a 
plate.  The  contacts  across  the  hard  rubber  rollers 
are  made  by  the  arc  shaped  bands  sliding  against 
the  ends  of  the  contact  springs ;  the  contacts  in  the 


164  -RAILWAY  SIGNALING 

indication  box  are  made  by  the  lug  fastened  to  the 
top  of  the  slide  bar  of  the  switch  and  lock  move- 
ment sliding  against  the  springs  in  the  box.  The 
reason  for  this  is  that  these  contact  pieces  are  most 
conveniently  made  of  brass  or  bronze.  Around  rail- 
roads there  are  always  certain  gases  in  the  air, 
thrown  off  by  the  combustion  of  coal,  which  gases 
have  a  corrosive  effect  on  most  metals,  and  brass 
in  particular.  The  product  of  this  corrosion  is  apt 
to  form  on  the  surface  of  the  contacts.  Some  of 
these  products  are  of  very  high  resistance  and  form 
a  serious  hindrance  to  the  ready  passage  of  elec- 
trical currents.  By  having  sliding  contacts  the  ac- 
tion of  one  brass  or  bronze  piece  against  the  other 
has  a  tendency  to  rub  off  these  products  and  to  keep 
the  contacts  bright. 


u 


Fig.  69. 

The  battery  used  with  electro-pneumatic  machines 
is  nowadays  invariably  a  storage  battery.  In  early 
installations  gravity  cells  were  used.  The  electric 
pressure  required  is  not  very  great,  from  12  to 
15  volts  being  ample.  Six  or  seven  storage  cells 
connected  in  series  is  sufficient  for  a  very  large 
plant.  These  cells  have  a  pressure  of  approximately 
2  volts  each  and  by  connecting  them  in  series 
the  sum  of  the  voltage  in  all  the  cells  is  made  the 
pressure  of  the  battery.  When  the  cells  of  a  bat- 
tery are  connected  in  series  the  positive  pole  of  one 
cell  is  connected  to  the  negative  pole  of  the  next  cell 
to  it,  the  positive  pole  of  that  again  is  connected  to 
the  negative  pole  of  the  one  ahead,  and  so  on 
throughout  the  battery.  The  last  positive  pole  is 


IN  THEORY  AND  PRACTICE.  165 

connected  to  the  outgoing  conductor,  and  the  in- 
coming conductor  is  connected  to  the  first  negative 
pole.  In  this  way  the  current  from  each  cell  flows 
through  every  cell  in  the  battery,  either  as  it  goes 
out  or  as  it  comes  in. 

The  conventional  method  of  showing  a  battery 
in  a  drawing  is  illustrated  in  Fig.  69.  The  long  line 
is  the  positive  side  of  each  cell,  and  the  short  heavy 
line  the  negative  side.  The  algebraic  sign  plus  is 
also  used  to  denote  the  positive  side  of  the  battery, 
and  the  algebraic  sign  minus  to  denote  the  negative 
side. 


CHAPTER  XIII. 

LOW    PRESSURE    PNEUMATIC    INTERLOCKING. 

Low  pressure  pneumatic  interlocking  attracted 
some  attention  in  this  country  several  years  ago, 
but  has  been  almost  lost  sight  of  since  the  introduc- 
tion of  all  electric  interlocking. 

It  appears,  however,  to  be  redivivus  in  Great  Brit- 
ain, the  British  Pneumatic  Railway  Signal  Com- 
pany having  taken  it  up  in  that  country,  and  a  brief 
description  of  this  system  here,  may,  therefore,  not 
be  amiss. 

The  fundamental  principles  in  which  it  differs 
from  the  electro-pneumatic  are  that  no  electricity  is 
required  in  its  operation,  and  that  its  work  is  done 
with  compressed  air  at  a  much  lower  pressure  than 
that  used  by  the  latter. 

The  first  feature,  the  absence  of  electricity,  was, 
at  one  time,  a  point  much  in  its  favor,  the  main- 
tenance of  electrical  devices  in  connection  with  sig- 
nal work  requiring  the  services  of  specially  trained 
men  who  a  few  years  ago  were  not  easily  obtain- 
able. At  the  present  time,  however,  as  so  much 
electrical  apparatus  is  used  in  other  ways  for  sig- 
naling purposes,  and  as  the  supply  of  expert  main- 
tainers  is  constantly  increasing,  so  that  competent 
men  may  always  be  had,  the  elimination  of  the  elec- 
trical feature  from  power  interlocking  would  in  most 

166 


IN  THEORY  AND  PRACTICE.  167 

cases  fail  to  reduce  the  cost  of  maintenance  to  any 
appreciable  extent. 

The  use  of  low  pressure  air  was  intended  to  pre- 
vent the  condensation  of  the  moisture  taken  into  the 
compressor  with  the  free  air  used  as  well  as  to 
economize  in  the  use  of  power  to  compress  it.  As 
an  offset  to  this  the  precautions  taken  to  prevent 
the  failure  of  the  electro  pneumatic  apparatus  from 
the  freezing  of  water  in  the  pipes  during  cold 
weather  appear  to  be  effective  and  the  fact  that  cyl- 
inders of  so  much  smaller  diameter  may  be  used 
without  diminishing  the  power  applied  to  the  move- 
ments, is  distinctly  in  its  favor. 

The  machine  used  with  the  low  pressure  pneu- 
matic is,  as  far  as  the  levers  and  locking  go,  very 
similar  to  that  used  with  the  General  Railway  Sig- 
nal Company's  (the  Taylor)  all  electric  machine, 
mention  of  which  was  made  in  the  chapter  on  lock- 
ing. The  locking  is  of  the  vertical  type.  The  tap- 
pets are  lowered  when  the  lever  is  reversed,  where- 
in the  locking  differs  from  the  all  electric  machine 
just  alluded  to,  in  which  the  tappets  are  raised  and 
the  levers  are  flat  bars  brought  down  to  a  square 
shank  on  the  end  of  which  is  a  vertical  handle  by 
which  they  are  pulled  out  from  the  body  of  the  ma- 
chine in  a  vertical  and  horizontal  plane  when  be- 
ing reversed,  and  shoved  in  when  being  returned  to 
normal. 

The  compressed  air  for  operating  the  switches, 
signals,  etc.,  is,  as  with  the  electro  pneumatic,  stored 
in  a  reservoir  at  some  convenient  place.  Four  pipes 
are  led  from  each  switch  lever  to  the  switch  it  op- 
erates and  three  from  each  signal  lever  to  the  sig- 
nal, in  addition  to  which  another  pipe  of  larger 
diameter  connects  the  switch  or  signal  cylinder 
through  the  medium  of  so-called  relay  valves,  with 
the  main  reservoir. 


168  RAILWAY  SIGNALING 

The  levers  have  two  slots  cut  in  the  flat  part 
which  slides  in  the  machine  frame.  The  slot  in 
front  operates  the  tappet  exactly  as  with  the  all 
electric  machine,  except  that  as  before  stated  the 
motion  is  reversed.  The  second  slot  serves  to 
make  the  indication  effective.  In  a  switch  lever 
which  we  will  first  describe  its  shape  forms  three 
sides  of  a  trapezoid,  one  side  being  parallel  to  the 
axis  of  the  lever  and  the  other  two  sides  forming 
equal  obtuse  interior  angles  with  the  first  side. 

A  cylinder  with  valves  arranged  to  admit  air 
from  either  end  is  placed  at  the  switch,  with  its 
piston  attached  to  a  motion  plate  switch  and  lock 
movement  very  similar  to  that  already  referred  to 
as  occasionally  used  with  the  electro  pneumatic. 
This  switch  and  lock  movement  besides  throwing 
and  locking  the  switch,  also  moves  a  slide  valve 
by  which  compressed  air  is  admitted  to  one  of  the 
pipes  leading  from  the  lever,  and  is  excluded  from 
another  one  which  is  connected  to  this  valve.  The 
compressed  air  being  alternately  admitted  to  and 
cut  off  from  these  pipes,  as  the  switch  is  in  full  re- 
verse or  full  normal  position,  and  locked  there. 

At  the  lever  end  each  of  these  pipes  is  connected 
with  a  separate  relay  valve  connecting  with  a  sep- 
arate cylinder  placed  beneath  the  lever.  The  piston 
rods  of  these  cylinders  extend  upward  and  termi- 
nate in  rollers  which  are  arranged  to  travel  in  the 
trapezoidal  slot  in  the  back  of  the  lever.  When  the 
lever  is  normal  the  roller  at  the  end  of  the  piston 
rod  of  the  forward  cylinder  is  at  the  far  forward 
end  of  the  slot  which  raises  it,  the  piston  rod  and 
its  piston  to  its  full  upward  stroke.  The  roller  of 
the  other  piston  rod  rests  on  the  lower  straight  part 
of  the  slot  and  is  then  at  the  lowest  point  of  its 
stroke.  These  are  the  indication  cylinders. 


IN  THEORY  AND  PRACTICE.  169 

Back  of  the  lever  and  attached  thereto  is  a  slide 
valve  controlling  a  connection  between  the  main 
reservoir  and  the  two  other  pipes  leading  from  the 
lever  to  the  switch  cylinder.  One  of  these  pipes 
connects  with  the  relay  valve  at  one  end  of  the  cyl- 
inder, and  the  other  with  the  relay  valve  at  the  other 
end  of  the  cylinder.  These  relay  valves  have  a  large 
8-inch  diameter  flexible  diaphragm,  so  that  a  very 
little  pressure  is  sufficient  to  move  their  pistons, 
which  have  a  stroke  of  about  a  quarter  of  an  inch 
only.  The  main  air  pipe  also  connects  with  each 
of  the  relay  valves. 

When  the  leverman  reverses  his  lever  it  is  stopped 
about  midway  of  the  stroke  by  the  roller  in  the  up- 
per end  of  the  piston  rod  of  the  back  indication  cyl- 
inder coming  in  contact  with  the  vertical  side  of 
the  end  of  the  horizontal  part  of  the  trapezoidal 
slot.  It  has  traveled  far  enough,  however,  to  have 
moved  the  slide  valve  to  which  the  back  of  the  lever 
is  attached  into  such  a  position  that  air  is  allowed 
to  flow  from  the  main  reservoir  along  the  pipe  lead- 
ing to  the  relay  valve  at  the  end  of  the  switch  cyl- 
inder at  which  its  piston  rests  when  the  switch  is 
normal.  This  air  is  admitted  through  a  much 
smaller  opening  than  the  diameter  of  the  pipe 
through  which  it  flows,  and  is,  therefore,  used  ex- 
pansively so  that  its  pressure  is  reduced  from  15 
pounds  per  square  inch  above  atmospheric  pressure, 
which  is  the  pressure  in  the  main  reservoir,  to  about 
7  pounds  per  square  inch.  At  the  relay  valve  this 
air  is  admitted  under  the  flexible  diaphragm,  there- 
by raising  its  piston  and  opening  a  connection  be- 
tween the  main  pipe  leading  from  the  reservoir  and 
the  switch  cylinder  back  of  the  latter's  piston.  The 
opposite  end  of  the  main  cylinder  being  opened  to 
allow  air  to  escape  from  it.  The  air  in  the  main 


170 


RAILWAY  SIGNALING 


pipe  which  is  at  full  pressure — 15  pounds  per  square 
inch — rushes  into  the  switch  cylinder  and  pushes 
the  piston  toward  its  other  end.  This  starts  the 
switch  and  lock  movement,  which  like  all  such  de- 
vices, first  unlocks  the  switch  and  raises  the  de- 
tector bar,  then  throws  the  switch  and  lastly  locks 
it  reversed  and  drops  the  detector  bar.  The  indica- 

" 


Fig.  70. 

tion  slide  valve  is  moved  by  the  first  and  third  po- 
sitions of  the  stroke  of  the  switch  and  lock  move- 
ment. 

The  first  movement  of  the  indication  slide  valve 
cuts  off  the  air  supply  from  the  indication  cylinders 


IN  THEORY  AND  PRACTICE.  171 

in  the  machine  through  the  relay  valves  in  the  ma- 
chine frame,  already  mentioned,  which  are  similar 
to  those  at  the  switch.  The  last  movement  which 
is  not  completed  until  the  switch  is  locked  reversed, 
admits  air  from  the  main  pipe  through  the  medium 
of  one  of  the  indication  relay  valves  in  the  machine 
to  the  rearmost  indication  cylinder,  tending  to  force 
its  piston  upward.  The  shape  of  the  back  end  of 
the  trapezoidal  slot  is  such  that  this  upward  pres- 
sure on  the  piston,  and  through  it  on  the  piston 
rod  of  the  rearmost  indication  cylinder,  forces  the 
lever  automatically  into  its  full  reversed  stroke 
without  the  aid  of  the  leverman,  and  unlocks  such 
other  levers  as  are  to  be  unlocked.  In  returning  the 
lever  to  normal  this  process  is  reversed,  except  that 
the  forward  indication  cylinder  comes  into  play  in- 
stead of  the  rear  one. 

Fig.  70  illustrates  diagramatically  this  operation. 
In  the  figure  a  is  the  lever,  b  is  the  operating  slide 
valve,  c  c  are  the  normal  and  reverse  indication  cyl- 
inders, d  d  are  their  respective  relay  valves,  e  e  are 
the  relay  valves  at  the  switch  cylinder,  f  is  the 
switch  cylinder  itself,  g  is  the  switch  and  lock  move- 
ment, h  is  the  indication  slide  valve,  i  i  i  and  j  j  j 
are  the  normal  arid  reverse  indication  pipes  re- 
spectively, k  k  k  and  1  1  1  are  the  normal  and  reverse 
operating  relay  valve  pipes,  m  m  m  is  the  main  air 
pipe  and  n  is  the  main  reservoir. 

Signal  mechanisms  are  much  the  same  as  switch 
mechanisms.  Like  the  electro  pneumatic,  signals 
only  indicate  from  the  normal  position.  In  fact,  this 
rule  is  general  to  all  forms  of  power  interlocking. 
As  there  is  only  one  indication,  the  rear  slot  in  the 
signal  lever  is  only  half  of  the  trapezoidal  form  of 
that  in  the  switch  lever.  There  is  but  one  indication 
cylinder  with  its  relay  valve  for  each  signal  lever 
in  the  machine. 


172 


RAILWAY  SIGNALING 


Fig.  71  shows  a  signal  lever,  signal  and  the  op- 
erating mechanism.  When  the  leverman  reverses 
the  lever  he  admits  air  at  7  pounds  pressure  along 
pipe  1  1  1  to  relay  valve  e.  This  valve  opens  the 
connection  between  main  pipe  m  m  m  and  the  lower 
end  of  cylinder  f.  The  air  from  pipe  m  m  m  being 
at  15  pounds  pressure,  pushes  up  the  piston,  clear- 
ing the  signal  blade.  There  being  no  indication 
from  this  movement  the  leverman  reverses  the  lever 
all  the  way  at  one  stroke. 


When  he  returns  the  lever  to  normal  again  it  is 
stopped  in  mid  stroke  by  the  roller  on  the  upper 
end  of  the  piston  rod  of  the  indication  cylinder.  Air 
is  being  admitted  to  relay  valve  e,  however,  by 
which  it  is  in  turn  admitted  to  indication  cylinder 
o,  and  from  there  to  the  upper  end  of  the  operating 
cylinder.  This  forces  the  piston  down  and  returns 
the  signal  to  normal.  When  at  full  normal  a  valve 
in  o  is  moved  so  as  to  admit  air  to  pipe  i  i  i,  which 
acts  on  the  indication  relay  valve  and  indication  cyl- 
inder exactly  as  in  the  case  of  a  switch. 


IN  THEOEY  AND  PRACTICE.  173 

Dwarf  signal  movements  are  identical  with  high 
signal  movements  in  principle,  though  differing 
slightly  in  detail  of  construction. 


CHAPTER  XIV. 

ALL  ELECTRIC  INTERLOCKING  GENERAL  RAILWAY  SIGNAL 
COMPANY'S  TYPE. 

With  all  electric  interlocking-  the  electric  current 
itself,  converted  into  mechanical  power  by  means 
of  electro  magnets  (it  is  here  to  be  understood  that 
the  shaft  of  an  electric  motor  is  made  to  revolve 
through  the  application  of  the  principles  of  magnet- 
ism), is  used  to  supply  the  power  by  which  the 
switches  and  signals  are  moved. 

Mechanical  power,  as  is  pretty  generally  known, 
is  measured  by  a  unit  called  a  horse  power.  A  horse 
power  is  that  force  required  to  raise  a  weight  of  33,000 
pounds,  one  foot  high  in  one  minute. 

Mechanical  power  supplied  by  an  electric  current 
acting  through  electro  magnets  is  not,  as  a  general 
thing,  measured  by  horse  power,  but  by  a  unit 
called  a  watt.  It  has  been  calculated  that  746  watts 
are  equal  to  one  horse  power. 

It  may  be  said  here  -  that  the  number  of  watts 
produced  by  any  battery  or  generator  is  equal  to  the 
product  of  the  number  of  volts  pressure  in  the  battery 
and  the  number  of  amperes  of  current  which  the 
battery  is  giving  forth.  A  battery  with  an  electric 
pressure  of  two  volts,  giving  forth  fifty  amperes  of 
current  would  be  able  to  perform  one  hundred  watts 
of  work,  or  a  little  less  than  one-seventh  of  a  horse- 
power. A  fifty  ampere  drain  on  a  battery  is  so  great 

174 


IN  THEOEY  AND  PRACTICE.  175 

that  it  would  require  the  renewing  of  a  primary  or 
recharging  of  a  storage  battery  at  very  frequent  in- 
tervals, so  that  it  has  been  found  to  be  much  more 
economical  to  increase  the  pressure  of  the  battery 
and  use  fewer  amperes.  Currents  delivered  under 
a  very  high  pressure  are  dangerous  to  persons  who 
may  be  accidentally  shocked  by  them,  and  it  has, 
therefore,  become  pretty  general  practice  to  use  110 
volt  batteries  for  all  electric  interlocking.  With 
the  type  we  are  now  concerned  with — the  General 
Railway  Signal  Company's,  the  battery  is  universally 
a  storage  battery  which  .receives  its  charge  from  a 
dynamo  driven  by  a  gasoline  engine,  or  by  an  elec- 
tric motor,  if  the  plant  is  so  situated  that  current  may 
be  had  from  an  electric  lighting  plant  or  electric  rail- 
way, with  which  to  drive  the  motor.  The  battery 
should  always  be  of  a  large  enough  capacity  in  am- 
pere hours  to  operate  the  plant  for  from  seven  to 
ten  days,  on  one  charge.  That  is,  it  should  be  only 
necessary  to  run  the  dynamo  once  every  seven  to  ten 
days. 

Such  an  arrangement  makes  the  furnishing  of 
power  for  these  plants  very  economical. 

The  quite  general  practice  is  to  place  the  battery 
in  the  lower  story  of  the  tower.  Where  a  gasoline 
engine  is  used  to  run  the  dynamo,  some  signal  en- 
gineers put  it  and  the  dynamo  in  a  separate  building, 
twenty-five  to  thirty  feet  away  from  the  tower,  in 
order  to  avoid  as  much  as  possible  the  chance  for  the 
destruction  of  both  generating  plant  and  battery  in 
case  the  engine  room  should  catch  fire.  Some  years 
ago  at  a  large  plant  in  Chicago,  which  was  arranged 
in  this  way,  the  engine  room  with  the  engine  and 
dynamo  were  burnt  up  the  day  after  a  charge  had 
been  given  the  battery.  The  plant  was  kept  in  oper- 
ation without  a  moment's  delay  on  this  charge  until 


176 


RAILWAY  SIGNALING 


a  new  engine  and  generator  were  procured  and  in- 
stalled. 

Other  signal  engineers  prefer  to  build  their  towers 
of  fire-proof  material  and  place  the  dynamo  and  en- 
gine in  its  basement,  as  well  as  the  battery. 

This  latter  practice  has  a  very  serious  objection 
in  the  fact  that  the  levermen  upstairs  are  now-a-days 
very  largely  dependent  on  the  use  of  the  telephone 
for  conducting  their  business,  and  the  noise  of  the 
engine  and  dynamo,  whenever  the  battery  is  being 
charged,  seriously  interferes  with  its  use. 


Fig.  72. 

The  machines  used  are  not  unlike  those  of  the  low 
pressure  pneumatic.  The  levers,  as  in  the  latter, 
are  slides  which  move  horizontally  backward  and  for- 
ward in  the  machine.  The  tappets  are  raised  up- 
ward to  perform  the  locking,  as  described  in  an  earlier 
chapter.  The  slide  valve  of  the  low  pressure  pneu- 
matic is  replaced  in  the  all  electric  by  a  double  cir- 
cuit controller  so  arranged  that  when  the  lever  is  nor- 


IN  THEORY  AND  PRACTICE.  177 

mal  (shoved  in)'  it  closes  one  circuit,  and  when  it  is 
reversed  (pulled  out)  it  opens  that  circuit  and  closes 
another  nearer  to  the  front  of  the  machine 

The  indication  cylinders  are  replaced  by  indication 
magnets,  and  below  the  indication  magnets  are  what 
are  known  as  safety  magnets,  the  use  of  which  will 
be  explained  a  little  further  on. 

Fig.  72  shows  three  views  of  one  of  these  ma- 
chines, and  also,  drawn  much  out  of  proportion  for 
the  sake  of  clearness  of  illustration,  at  the  lower  side 


tm 

I 

H 

Fig.  73. 

of  the  plate  one  of  the  circuit  controllers  which  the 
levers  operate. 

But  one  style  of  switch  operating  machine  is  used 
with  this  type  of  interlocking.  It  may  be  applied 
to  switches,  derails  or  movable  frogs.  This  switch 
machine  differs  materially  from  anything  yet  de- 
scribed, so  that  we  will  now  give  a  detailed  explan- 
ation of  it. 


178  RAILWAY  SIGNALING 

Fig.  73  illustrates  one  of  these  machines  in  plan 
and  section,  showing  its  connections  with  a  switch  and 
detector  bar. 

A  is  a  small  electric  motor.  B  is  an  arrangement 
of  gears  operated  by  the  shaft  of  the  motor  through 
the  means  of  which  the  speed  of  the  last  gear  in  the 
combination  is  much  slower  than  that  of  the  motor 
shaft  and  power  is  gained  proportionately. 

This  power  is  transmitted  to  a  cam  crank  C,  the 
lower  arm  of  which  is  connected  by  a  special  switch 
adjustment  to  the  head  rod  of  the  switch.  The  main 
gear  of  the  combination  B,  shown  as  b  in  the  draw- 
ing, has  a  crank  pin  fastened  in  its  side,  which  not 
only  serves  to  operate  the  cam  crank,  but  is  also 
joined  by  a  connecting  rod  c  to  one  arm  of  a  three 


Fig.  74. 

arm  crank  D,  another  arm  of  which  is  connected  by 
a  link  to  a  straight  arm  compensator  through  whose 
medium  it  throws  the  detector  bar.  The  third  arm 
of  this  three  arm  crank  D  is  connected  by  a  specially 
shaped  link  to  a  double  lock  plunger,  which  is  shown 
in  Fig.  74.  It  will  be  noticed  that  the  throw  rod 
of  the  switch,  one  end  of  which  is  connected  to  the 
cam  crank  C  and  the  other  end  of  which  terminates 
in  the  special  switch  adjustment,  is  flattened  where 
it  passes  the  center  of  the  three  arm  crank  support. 
One  point  of  the  lock  plunger  passes  through  a  hole 
in  this  flattened  part  of  the  throw  rod,  and  the  other 
point  passes  through  a  hole  in  the  regular  lock  rod, 
just  as  is  the  case  with  any  facing  point  lock,  so  that 
the  switch  points  are  double  locked. 


IN  THEOEY  AND  PRACTICE.  179 

E  is  a  pole  changing  switch  operated  by  a  small 
lever  c,  which  is  engaged  by  two  small  lugs  on  top 
of  the  lock  rod,  so  that  when  the  switch  is  normal  the 
end  of  this  lever  which  is  engaged  by  these  lugs  is 
thrown  away  from  the  center  of  the  track,  and  when 
the  switch  is  reversed  it  is  thrown  toward  the  center 
of  the  track.  The  motion  of  this  lever  is  transmitted 
by  the  operating  rod  f  to  the  pole  changer  F,  after 
the  lock  plunger  has  passed  through  the  lock  rod> 
but  not  until  then.  The  use  of  this  pole  changer 
will  be  explained  presently. 

The  motor  B  is  constructed  with  a  double  set 
of  what  are  known  as  field  coils.  It  is  by  passing 
a  current  through  these  field  coils  that  the  revolving 
part  of  the  motor,  called  the  armature,  is  made  to 
revolve;  being  keyed  to  the  shaft  it  turns  that  also. 
One  set  of  these  field  coils  when  energized  causes 
the  motor  to  revolve  in  one  direction,  and  the  other 
set  causes  it  to  revolve  in  the  other  direction.  Part 
of  the  function  of  the  pole  changer  is  to  switch  the 
path  for  the  current  from  the  battery  from  one  set 
of  the  field  coils  to  the  other. 

In  the  back  of  the  machine  are  three  brass  bars 
54  "x/^"  in  section,  laid  horizontally  parallel  to  each 
other  in  the  same  vertical  plane.  These  are  called 
bus  bars,  and  perform  the  same  function  that  the  bat- 
tery strips  on  the  combination  plate  of  an  electro 
pneumatic  machine  perform,  namely,  to  make  a  con- 
venient common  means  of  connecting  the  external 
circuits  with  the  positive  or  negative  poles  of  the 
battery.  The  upper  one  of  these  bus  bars  is  used 
exclusively  for  control  wires  leading  out  to  switch 
machines,  the  middle  one  for  indication  wires,  and 
the  lower  one  for  control  wires  leading  to  signals, 
and  are  known  respectively  as  the.  switch  bus  bar, 
the  indication  bus  bar,  and  the  signal  bus  bar.  There 
are  two  common  wires  known  as  the  main  common 


180  RAILWAY  SIGNALING 

and  the  indication  common.  The  main  common  runs 
through  the  entire  plant.  The  indication  common 
is  cut  into  various  sections  which  are  joined  to  the 
main  common  which  connects  to  the  negative  pole 
of  the  battery.  The  main  common  wire  does  not 
connect  with  the  bus  bar,  the  switch  and  signal  bus 
bars  being  used  exclusively  for  out  going  currents 
from  the  battery.  As  will  shortly  be  explained,  in- 
coming currents  from  another  source  of  electric 
energy  pass  through  the  indication  bus  bar. 

There  are  two  control  wires,  known  as  the  nor- 
mal and  the  reverse  control  leading  from  the  inter- 
locking machine  to  the  motor  in  the  switch  machine. 

When  the  leverman  commences  to  reverse  his  lever, 
its  stroke  is  arrested  as  already  described  by  the  in- 
dication dogs  until  the  indication  magnet  is  energized, 
but  it  is  completed  far  enough  to  close  the  circuit 
through  the  reverse  control  wire  and  one  set  of  field 
coils  in  the  switch  motor.  This  starts  the  motor 
shaft  revolving  and  through  the  gearing  revolves 
the  main  gear  b  in  the  direction  of  the  arrow  in  the 
sectional  view  of  the  switch  machine  in  Fig.  73. 

The  action  of  the  cam  crank  is  very  similar  to  that 
of  the  escapement  crank  in  a  mechanical  switch  and 
lock  movement,  that  is,  the  first  part  of  the  move- 
ment of  the  main  gear  does  not  move  the  crank  arm. 
The  crank  pin,  however,  being  rigidly  fastened  to  the 
side  of  the  main  gear  commences  to  move  the  con- 
necting rod,  and  through  it  the  three  arm  crank,  at 
once,  thereby  raising  the  detector  bar  and  withdraw- 
ing the  locking  plunger  from  engagement  with  the 
lock  rod  and  throw  rod  of  the  switch.  In  passing, 
it  may  as  well  be  noted,  that  with  this  switch  move- 
ment, the  detector  bar  does  not  go  entirely  over. 
It  is  raised  up  by  the  three  arm  crank  and  then  drops 
back  on  the  same  side  of  the  vertical  from  which  it 
came  up.  After  the  locking  plunger  is  withdrawn, 


IN  THEOEY  AND  PRACTICE.  181 

the  crank  pin  engages  the  cam  end  of  the  cam  crank 
and  throws  the  switch  points,  after  which  the  crank 
pin  ceases  to  move  the  crank  arm,  but  still,  through 
the  connecting  rod,  moves  the  three  arm  crank  so 
as  to  lock  the  switch  reversed  and  drop  the  detector 
bar.  As  soon  as  this  is  accomplished  the  crank  pin 
engages  the  semi-circular  corner  of  the  cam  slot, 
shown  as  X,  which  stops  the  further  progress  of  the 
main  gear  in  the  direction  in  which  it  is  then  moving. 
This  does  not,  however,  stop  the  motor,  because  the 
motor  shaft  is  divided  and  is  held  together  by  a  fric- 
tion clutch  which  slips  as  soon  as  the  further  motion 
of  the  main  gear  is  checked.  The  action  of  the  pole 
changing  switch  as  the  track  switch  was  reversed  has 
been  such  as  to  cut  the  current  from  the  battery  off 
from  the  field  coils  of  the  motor. 

Now  as  stated  in  the  commencement  of  our  con- 
sideration of  power  interlocking,  a  motor  while  re- 
volving is  generating  a  small  amount  of  electric  cur- 
rent in  opposition  to  the  current  which  is  being  sup- 
plied to  run  the  motor,  which  fact  is  utilized  here  to 
operate  the  indication.  The  battery  current  having 
been  shut  off  from  the  motor  by  the  action  of  the 
pole  changing  switch  and  pole  changer,  does  not 
instantly  stop  the  motor,  because  it  has  acquired 
enough  momentum  to  continue  revolving  for  some 
little  time,  and  is  thereby  generating  a  current  of 
an  opposite  polarity  (flowing  in  the  opposite  direc- 
tion) from  the  current  which  operated  the  motor. 

The  action  of  the  pole  changer  has  been  such  also 
as  to  close  a  circuit  by  which  this  current  which  is 
being  generated  by  the  motor  may  flow  back  toward 
the  machine  along  the  wire  which  a  moment  before 
was  the  normal  control  wire.  This  current  flows 
back  through  the  indication  magnet,  to  the  indication 
bus  bar  and  from  thence  to  the  indication  common 
wire  by  which  it  finds  its  way  back  to  the  negative 


182  RAILWAY  SIGNALING 

pole   of  the   switch   motor,   acting  temporarily   as   a 
dynamo. 

This  is  known  as  a  dynamic  indication  current,  as 
distinguished  from  a  battery  current.  It  is  peculiar 
to  the  type  of  machine  we  are  now  discussing. 

Signal  mechanisms  also  vary  greatly  from  any  we 
have  yet  discussed. 

In  every  variety  of  all  electric  interlocking  there 
is  always  a  possibility  that  wrong  currents  may  pass 
through  a  wire.  This  may  happen  from  various 
causes.  Two  wires,  one  of  which  is  already  carrying 
a  current  from  the  battery,  may  touch  each  other, 
so  that  the  current  may  divide  and  part  of  it  go 
through  each  wire,  or  a  wire  carrying  a  current  from 
another  source,  such  as  a  telephone,  telegraph  or 
trolley  wire  may  touch  earth  or  some  other  conductor 
which  will  make  a  connection  between  it  and  one 
connected  with  the  interlocking  plant  not  at  that  time 
intended  to  be  in  circuit. 

Troubles  from  the  first  cause  are  called  crosses,  and 
from  the  latter,  interferences  by  foreign  currents. 

Where  plants  are  near  power  houses  or  lines  of 
electric  railways  or  lighting  plants,  currents  of  very 
high  pressure  are  often  found  going  through  the 
earth,  part  of  which  may  leave  it  and  run  through 
any  wire  which  touches  the  earth,  provided  the  cur- 
rent can  find  a  path  out  again.  These  are  called 
earth  currents. 

To  have  any  wrong  current  of  this  sort  come 
through  an  indication  magnet  or  start  a  switch  motor 
when  the  leverman  did  not  intend  it  should  be  started 
might  lead  to  very  serious  trouble,  so  that  the  utmost 
precautions  must  be  taken  to  prevent  such  action  by 
these  false  currents. 

It  is  for  this  reason  that  the  safety  magnet  already 
alluded  to  is  introduced.  The  current  from  the  bat- 
tery which  operates  the  switch  motor  is  made  to  pass 


IN  THEORY  AND  PRACTICE.  183 

through  this  magnet,  which  is  placed  immediately  be- 
neath the  indication  magnet  in  such  a  way  that  the 
armature  of  the  indication  magnet  rests  on  the  end 
of  the  cores  of  the  safety  magnet.  Now  if  a  cur- 
rent is  flowing  through  either  control  wire  this  safety 
magnet  is  energized  and,  therefore,  holds  down  on 
the  armature  of  the  indication  magnet  with  much 
greater  force  than  the  indication  magnet  can  exert 
to  pull  it  up.  After  passing  through  the  safety  mag- 
net the  battery  connection  is  divided  into  the  normal 
and  the  reverse  control  wires.  Each  of  these  passes 
through  another  separate  magnet.  These  have  a  com- 
mon armature  and  taken  together  and  with  the  arma- 
ture form  what  is  known  as  the  indication  selector. 
When  the  lever  is  reversed  the  reverse  control  cir- 
cuit is  closed,  and  not  only  the  safety  magnet,  which 
is  common  to  both  normal  and  reverse  control  wires, 
but  also  that  one  of  the  indication  selector  magnets 
which  is  in  the  reverse  control  circuit,  are  both  ener- 
gized. The  energizing  of  the  selector  magnet  at- 
tracts the  common  armature  toward  it.  This  arma- 
ture is  arranged  as  a  lever,  being  hinged  at  one  end. 
The  free  end  plays  between  two  contact  points.  When 
it  is  attracted  toward  one  of  its  magnets,  it  touches 
one  of  these  contact  points,  and  when  it  is  attracted 
toward  the  other  it  leaves  the  first  contact  point  and 
touches  the  second.  These  contact  points  are  made 
part  of  the  normal  and  reverse  indication  circuits.  The 
hinge  of  the  armature  is  connected  to  the  indication 
magnet.  Now  when  the  battery  current  flows  through 
the  reverse  control  wire  that  magnet  is  energized  and 
its  armature  closes  the  reverse  indication  circuit, 
ready  to  receive  the  indication  current  just  as  soon 
as  the  pole  changer  at  the  switch  machine  acts.  If, 
however,  foreign  current  is  flowing  in  the  normal 
control  wire,  the  instant  the  pole  changer  breaks  the 
circuit  through  the  reverse  control  wire  the  common 


184 


RAILWAY  SIGNALING 


armature  is  pulled  away  from  the  magnet  in  that 
circuit  by  the  magnet  in  the  normal  circuit,  and  the 
reverse  indication  circuit  is  broken,  so  that  nothing 
but  the  proper  current  can  effect  the  indication. 

In  addition,  also,  so-called  fuses  are  let  into  the 
control  circuits.  These  fuses  are  short  lengths  of 
fine  fusible  wire.  It  is  a  fact  that  when  the  pressure 
of  a  battery  or  generator  is  forcing  current  through 
a  conductor  of  high  resistance,  the  current  tends  to 
heat  the  conductor.  The  fuses  are  so  arranged  that 
in  case  a  switch  should  stick  or  the  points  become 
blocked,  and  the  friction  clutch  should  fail  to  slip, 
the  increased  current  which  will  be  poured  in  from 
the  battery  to  the  motor  will  so  heat  the  wire  that 


it  will  fuse  or  melt  away,  thus  automatically  opening 
the  circuit  and  preventing  the  increase  of  current 
from  heating  the  magnets  or  field  coils  to  such  an 
extent  as  to  burn  the  insulation  off  the  wires  and 
ruin  them. 

Fig.  75  shows  a  switch  lever,  indication  and  safety 
magnets,  indication  selector,  switch  machine  and  con- 
nections, in  a  diagrammatic  way,  which  will  no  doubt 
aid  the  reader  in  tracing  out  the  foregoing  descrip- 
tion. Even  with  all  the  safeguards  just  described 
the  reader  can  no  doubt,  if  he  gives  the  matter  enough 
study,  devise  a  combination  of  crosses  which  might 
give  a  false  indication,  but  the  possibilities  of  such 
happening  in  actual  practice  are  so  very  unlikely  as 
to  be  considered  outside  of  the  calculation. 


IN  THEORY  AND  PRACTICE. 


185 


High  signals  as  made  at  present  usually  have  the 
operating  machinery  in  a  case  at  the  base  of  the  pole, 
which  is  virtually  an  enlargement  thereof.  In  the 
earlier  design  the  operating  machinery  was  placed 
in  a  separate  case  attached  to  the  side  of  the  pole. 
As  a  great  many  signals  so  constructed  are  still  in 
service,  I  shall  take  space  to  describe  both  designs. 
The  former  is  known  as  an  inside  connected  signal, 
and  the  latter  as  an  outside  connected  signal.  As  the 
latter  was  the  earlier  design  we  shall  describe  it  first. 


Fig.  76. 

Fig.  76  shows  a  side  and  end  view  of  a  signal 
machine  for  an  outside  connected  signal.  A  is  the 
motor,  B  the  system  of  gearing,  much  like  that  in  a 
switch  machine,  terminating  in  a  chain  wheel  b  to 
which  a  chain  is  attached,  the  other  end  of  which  is 
fastened  to  the  balance  lever  on  the  signal  pole  from 
which  the  up  and  down  rod  leads  to  the  arm  plate. 
For  one  arm  signals  the  motors  supplied  are  not  re- 
versible, for  two  arm  signals  they  are.  With  a  one 
arm  signal  one  wire  runs  from  the  machine  to  the 
motor.  The  action  of  the  motor  clears  the  signal, 
which  is  restored  to  normal  by  the  counterweight. 
A  magnetic  brake  shown  as  a  in  the  figure  is  pro- 


186  EAILWAY  SIGNALING 

vided  and  so  arranged  that  when  the  signal  arm  has 
reached  the  full  clear  position  a  circuit  controller  at- 
tached to  the  up  and  down  rod  and  operated  by  it, 
switches  the  current  from  the  motor  to  the  coils  of 
the  brake  magnet.  This  causes  the  brake  shoe  to 
bear  on  the  brake  wheel  and  stop  the  motor  very 
quickly.  The  chain  is  attached  to  the  counterweight 
lever  by  a  spring  jaw,  shown  in  Fig.  77,  which  al- 
lows the  motor  to  over  run  a  few  turns  without  being 
suddenly  brought  up  by  the  arm  plate  coming  in 
contact  with  its  stop.  Current  is  kept  on  the  brake 


Fig.  77. 

magnets  while  the  signal  remains  in  the  clear  position. 
Their  coils  are  so  constructed  as  to  have  a  very  high 
resistance,  thereby  drawing  a  minimum  of  current 
from  the  battery  while  the  signal  is  clear.  When  the 
leverman  returns  the  lever  to  normal  the  circuit 
through  the  brake  coils  is  opened,  the  brake  lets  go, 
and  the  counterweight  not  only  throws  the  blade  to 
normal,  but  acting  through  the  chain  on  the  chain 
wheel,  spins  the  shaft  of  the  motor  around  in  a  direc- 
tion opposite  to  that  in  which  it  revolved  when  wind- 
ing up  the  chain  in  order  to  clear  the  signal.  As 
stated  when  we  commenced  discussing  power  inter- 
locking, a  motor  revolving  in  a  reverse  direction  be- 
comes a  dynamo.  As  soon  as  the  signal  blade,  there- 
fore, reaches  its  normal  position  the  control  wire 
circuit  is  closed  through  the  circuit  controller  on 
the  up  and  down  rod,  but  being  shifted  to  the  indi- 
cation circuit  by  the  circuit  controller  at  the  lever, 
the  dynamic  current  generated  in  the  motor  flows 
through  the  indication  magnet,  energizes  it,  and  re- 


IN  THEOET  AND  PRACTICE.  187 

leases  the  lever  so  that  its  stroke  may  be  completed. 
Two  bladed  signals  of  this  type  are  generally  selected 
by  a  circuit  controller,  called  a  switch  box,  or  selec- 
tor, attached  to  the  points  of  the  switch.  The  com- 
mon wire  from  the  lever  runs  to  this  switch  box, 
where,  if  the  switch  is  normal,  it  is  connected  to  a 
wire  running  into  one  set  of  field  coils  in  the  motor, 
and  if  the  switch  is  reversed,  it  is  connected  to  a  wire 
running  to  another  set  of  field  coils.  The  first  set 
will  revolve  the  motor  one  way  and  the  second  set 
will  revolve  it  in  the  opposite  direction.  The  chain 
instead  of  being  pinned  to  the  chain  wheel,  as  with 
the  single  blade  signal,  passes  over  it,  where  it  is 
prevented  from  slipping  by  sprockets.  One  end  of 
the  chain  is  fastened  to  the  counterweight  lever  of 
the  upper  blade,  and  the  other  end  to  the  counter- 
weight lever  of  the  lower  blade.  Now  if  the  motor 
revolves  in  one  direction  it  will  by  the  sprocket  in 
the  rim  of  the  chain  wheel  pull  up  on  one  end  of  the 
chain  and  slack  away  on  the  other.  It  will,  there- 
fore, raise  one  counterweight  lever  but  leave  the 
other  one  down.  The  indication  current  is  generated 
in  the  same  manner  as  described  for  a  single  blade 
signal. 

Where  more  than  two  blades  on  one  mast  are  to  be 
operated  by  one  lever  a  special  hook  selector  is  at- 
tached to  the  mast.  The  motor  then  used  is  the  same 
as  for  a  single  arm  signal.  The  chain  is  attached 
to  an  operating  lever  much  like  a  counterweight  lever. 
This  is  keyed  to  a  shaft  on  which  the  counterweight 
levers  are  also  pivotted,  but  are  not  keyed  thereto. 
Outside  of  the  last  counterweight  lever  a  so-called 
short  operating  lever  is  keyed.  These  two  operating 
levers  are  connected  by  a  latch  bar.  Over  each  of 
the  counterweight  levers  is  a  pair  of  electro  magnets 
coupled  together  to  act  on  an  armature  which  is  bent 
around  so  as  to  form  a  hook.  When  any  one  pair 


188 


RAILWAY  SIGNALING 


of  magnets  is  energized  it  attracts  its  armature,  the 
hook  of  which  engages  the  latch  bar.  The  switch 
box  selects  the  pair  of  magnets  to  be  energized. 


Fig.  78. 


The  chain  from  the  motor  is  attached  to  the  long 
operating  lever,  which,  on  being  raised  by  the  chain, 
brings  with  it  that  one  of  the  counterweight  levers 
whose  magnets  happen  to  be  energized  at  the  time. 


IN  THEORY  AND  PRACTICE.  189 

At  the  switch  box  the  different  magnet  circuits  as 
they  are  called  in  play  are  connected  to  the  common 
wire.  In  this  way  the  current  goes  out  to  the  magnet 
first  and  returns  by  way  of  the  switch  box. 

The  mechanism  for  an  inside  connected  high  signal 
is  shown  in  Fig.  78. 

The  motor  A  is  so  placed  that  its  shaft  stands  ver- 
tically. This  shaft  turns  a  screw  which  shoves  up 
on  the  cross  head  B.  This  cross  head  is  connected 
to  the  up  and  down  rod  so  that  when  it  is  shoved  up 
the  arm  plate  of  the  signal  is  brought  to  the  clear 
position.  Its  movement  also  mechanically  operates 
circuit  controllers  by  which  the  battery  current  is 
switched  from  the  field  coils  of  the  motor  through 
high  resistance  magnet  coils  operating  a  brake  which 
bears  on  the  motor  shaft,  holding  the  signal  at  clear. 

When  the  leverman  returns  the  lever  to  normal, 
circuit  through  the  brake  magnet  is  opened ;  it  releases 
its  armature,,  thereby  relieving  the  pressure  of  the 
brake  shoe  on  the  shaft.  The  weight  of  the  cross 
head  pressing  down  on  the  thread  of  the  screw  spins 
the  motor  shaft,  and  with  it  the  motor  armature, 
around  in  the  direction  opposite  to  that  in  which  it 
turned  while  setting  the  signal  at  clear,  thereby  gener- 
ating the  indication  current. 

In  the  case  of  a  two  or  three  bladed  signal  the 
selection  is  done  through  a  switch  box,  the  circuits 
from  which  are  carried  through  magnets  in  the  motor 
case.  These  magnets  are  attached  to  the  cross  head 
and  move  with  it.  When  energized  their  armatures 
operate  hooks,  much  like  those  in  an  ordinary  me- 
chanical selector,  which  engage  notches  in  the  lower 
ends  of  the  up  and  down  rods.  Thus  the  movement 
of  the  cross  head  is  transmitted  to  that  one  of  the 
up  and  down  rods  which  is  hooked  to  it  at  the  time. 

Before  describing  the  dwarf  signal  movement  used 
with  the  General  Railway  Signal  Company's  appa- 
ratus, it  will  be  necessary  to  explain  that  if  the  core 


190  RAILWAY  SIGNALING 

of  an  electro  magnet  is  loose  in  the  coil  and  is,  while 
the  coil  is  de-energized,  partially  withdrawn,  the  coil 
will  when  energized  act  on  the  core  as  a  magnet  and 
tend  to  pull  it  completely  back  into  the  opening 
through  its  own  center.  In  this  way  the  core  may 
be  made  to  perform  the  same  work  as  is  performed 
by  the  armatures  of  such  magnets  as  we  have  dis- 
cussed heretofore,  and  a  considerably  longer  stroke 
can  be  had.  Such  an  arrangement  is  known  as  a 
solenoid. 

The  General  Railway  Signal  Company's  dwarf  sig- 
nals are  operated  by  solenoids  instead  of  by  motors. 
The  magnets  of  these  solenoids  are  placed  inside  the 
mechanism  case  of  the  signal  and  encircle  tubes  inside 
of  which  the  cores,  which  are  attached  to  the  cross  head 
move.  A  shaft  from  the  upper  side  of  the  cross 
head  terminates  in  a  rack,  which  engages  a  pinion 
keyed  to  the  spindle  to  which  the  arm  plate  is  also 
attached,  so  that  the  up  and  down  movement  of  the 
cross  head  imparts  a  rotary  movement  to  the  spindle, 
thereby  operating  the  arm  plate. 

Sliding  circuit  controllers  much  like  those  used  with 
the  electro  pneumatic  signal  serve  to  switch  the  bat- 
tery current  from  the  solenoid  coils  to  the  indication 
circuit  when  the  signal  is  returned  to  normal.  These 
dwarf  signals,  therefore,  use  battery  and  not  dynamic 
current  for  their  indications. 

In  the  operating  room  of  each  tower  is  placed  an 
ammeter,  which  is  an  instrument  to  gauge  the  number 
of  amperes  of  current  being  used  at  any  particular 
time,  and  a  voltmeter,  which  is  an  instrument  to 
gauge  the  pressure  in  the  battery  at  all  times,  just 
as  a  steam  gauge  is  used  to  gauge  the  pressure  of 
steam  in  a  boiler. 

When  a  plant  is  in  good  order  and  no  current  is 
being  lost  through  leaks  the  ammeter  should  register 
zero,  except  while  a  switch  is  being  moved  or  a  signal 


IN  THEORY  AND  PRACTICE.  191 

is  at  clear.  The  voltmeter  should  register  approx- 
imately 110  volts  at  all  times,  except  while  the  battery 
is  being  charged  when  it  will  register  much  higher. 
If  it  falls  much  below  that  point  it  is  an  indication 
that  the  battery  should  be  charged  at  once. 

A  power  board  is  placed  in  the  room  with  the 
dynamo.  This  is  also  provided  with  an  ammeter, 
a  voltmeter,  with  incandescent  lamps  which  light  up 
in  case  of  leakages,  and  with  safety  switches  which 
throw  themselves  automatically  and  break  circuit  in 
case  such  an  amount  of  current  as  would  endan- 
ger the  magnet  coils  by  overheating  them  should 
chance  to  get  into  one  or  more  of  the  circuits.  These 
power  boards  are  not  peculiar  to  interlocking  plants, 
and  they  are  in  all  essential  details  similar  to  those 
used  at  any  power  station. 


CHAPTER  XV. 

OTHER    TYPES    OF    POWER    INTERLOCKING. 

Before  entering  on  a  description  of  the  Union 
Switch  and  Signal  Company's  all  electric  interlocking 
apparatus,  there  is  another  point  in  regard  to  the  ap- 
plication of  electric  currents  which  I  shall  call  to  the 
reader's  notice. 

Heretofore  we  have  considered  only  direct  current 
electricity,  by  which  is  meant  electricity  which  flows 
always  in  one  direction. 

Certain  types  of  generators  or  dynamos  are  so  con- 
structed that  they  give  forth  a  current  which  flows 
first  in  one  direction  and  then  in  the  other.  That 
is,  what  would  be  the  positive  pole  in  a  direct  current 
generator  becomes  in  an  alternating  current  genera- 
tor first  the  positive  and  then  the  negative,  and  the 
negative  pole  is  also  first  negative  and  then  positive. 
The  transition  from  one  to  the  other  is  very  rapid. 
The  direction  of  the  current  is  changed  as  often  as 
200  times  a  second.  Instruments  known  as  trans- 
formers are  manufactured,  which  will  either  raise  or 
lower  the  pressure  of  an  alternating  current,  but  as 
the  principles  by  which  such  instruments  perform  their 
function  belong  more  to  electrical  science  than 
to  railway  signaling,  I  shall  not  go  into  them 
here.  The  reader  who  wishes  to  pursue  this  subject 
further  will  find  it  fully  explained  in  any  treatise  on 
alternating  current  apparatus.  When  the  pressure 
of  a  current  is  raised  by  a  transformer  it  is  said  to  be 

192 


IN  THEORY  AND  PRACTICE.  193 

stepped  up,  and  when  it  is  lowered,  to  be  stepped 
down. 

Where  in  a  discussion  both  direct  and  alternating 
currents  are  being  mentioned,  it  is  customary  to  write 
the  initials  D.  C.  and  A.  C.  after  the  description  of 
the  current,  as  110  volts  D.  C.  or  110  volts  A.  C.,  as 
the  case  may  be. 

Where  only  direct  current  is  being  considered  in 
a  discussion  these  initials  are  omitted. 

With  alternating  currents  it  is  customary  always  to 
retain  them. 

The  machines  used  with  the  Union  Switch  and  Sig- 
nal Company's  all  electric  interlocking  are  very  sim- 
ilar indeed  to  those  used  with  the  electro-pneumatic. 
The  contact  strips  and  battery  strips  being  intended 
to  carry  currents  under  an  electric  pressure  of  110 
volts  are  made  much  heavier  than  those  for  the  electro 
pneumatic  machine,  which  carry  current  under  pres- 
sure of  only  10  to  15  volts. 

The  indication  jaw  is  not  operated  directly  by  an 
indication  electro  magnet  as  in  the  electro  pneumatic 
machine.  It  is  attached  to  a  centrifugal  device  very 
much  like  the  familiar  governor  of  a  stationary  en- 
gine, consisting  of  two  stems  terminating  in  com- 
paratively heavy  balls  and  hinged  at  the  other  ends 
to  a  vertical  shaft.  When  this  shaft  is  revolved  rapidly 
the  balls  have  a  tendency  to  separate,  caused  by  cen- 
trifugal force.  At  rest  the  stems  form  a  figure  like 
the  two  sides  of  a  triangle,  but  on  being  revolved 
rapidly  they  move  into  a  horizontal  straight  line 
through  the  apex  of  the  triangle,  thus  raising  the  balls 
and  the  jaw  which  is  attached  to  them  and  releasing 
the  indication  segment.  The  stems  and  balls  are  at- 
tached to  the  shaft  of  a  small  alternating  current  motor 
placed  in  the  back  of  the  machine  and  so  arranged 
that  its  shaft  is  vertical.  In  front  of  this  motor  is  a 
transformer,  which  in  turn  is  connected  by  proper 


194  RAILWAY  SIGNALING 

wiring,  which  will  soon  be  explained,  to  the  switch  or 
signal  moving  machinery. 

The  switch  machine  consists  of  a  motor,  the  shaft 
of  which,  through  the  medium  of  a  reducing  gear, 
revolves  a  cam  screw.  The  reducing  gear  is  so  ar- 
ranged that  twenty-five  revolutions  of  the  motor  give 
one  revolution  to  the  cam  screw.  The  main  shaft 
is  divided  and  its  parts  are  held  together  by  a  clutch, 
the  two  parts  of  which  are  forced  against  each  other 
by  electro  magnets,  and  is,  therefore,  known  as  a 
magnetic  clutch. 

The  spiral  around  the  cam  screw  engages  rollers 
attached  to  the  ends  of  one  arm  of  each  of  two  sepa- 
rate cranks.  The  other  arm  of  one  of  these  cranks  is 
attached  by  a  special  switch  adjustment  to  the  head 
rod  of  the  switch.  The  outside  arm  of  the  other 
crank  is  attached  to  the  detector  bar,  and  the  same 
arm  which  engages  the  cam  screw  is  attached  to  a 
slide  plate  which  extends  beyond  the  end  of  the  main 
shaft  and  carries  the  locking  dogs,  which  engage  the 
lock  rod  attached  to  the  switch  points.  The  motor 
is  so  arranged  that  after  a  switch  has  made  its  com- 
plete travel  and  is  locked,  the  clutch  releases  and  the 
driving  current  is  switched  to  another  circuit  (still 
operating  the  motor)  in  such  a  way  that  instead  of 
being  a  current  of  uniform  pressure  it  pulsates.  When 
the  lever  is  reversed  current  from  the  battery,  which 
is,  as  with  the  General  Railway  Signal  Company's 
machine,  a  110  volt  storage  battery,  is  supplied  to  the 
motor  and  starts  it  revolving,  carrying  with  it  the 
cam  screw.  This  moves  the  slide  plate  carrying  the 
dogs,  and  unlocks  the  switch,  at  the  same  time  throw- 
ing the  detector  bar  all  the  way  over.  Next  the 
switch  is  thrown  while  the  points  are  not  locked,  and 
lastly  the  reverse  locking  dog  engages  the  lock  rod 
the  same  as  with  any  other  type  of  switch  and  lock 
movement.  As  soon  as  the  switch  is  over  and  locked  a 


IN  THEORY  AND  PRACTICE.  195 

circuit  controller,  mechanically  operated  by  the  switch 
and  lock  movement,  switches  the  circuit  through  the 
motor  as  above  described.  As  long  as  the  current 
in  this  circuit  was  of  uniform  pressure  it  had  no  effect 
on  the  transformer  through  which  it  is  carried,  but 
as  soon  as  it  becomes  a  pulsating  current  it  produces 
a  perfect  alternating  current  in  the  other  side  of  the 
transformer.  This  secondary  current  is  carried 
through  the  indication  motor  and  starts  the  latter 
motor  revolving,  thereby  through  the  governor-like 
apparatus  already  described,  releasing  the  indication 
segment.  The  leverman  then  completes  the  stroke  of 
the  lever,  thus  breaking  the  circuit  through  the  switch 
motor,  which  stops  revolving. 

As  in  the  General  Railway  Signal  Company's  ma- 
chine, one  common  control  wire  and  one  common 
indication  wire  are  carried  through  each  plant,  and 
there  are  two  control  wires  to  each  switch  move- 
ment which  also  serve  as  indication  wires.  The  fea- 
ture of  an  alternating  current  indication  has  been 
introduced  to  prevent  the  possibility  of  any  stray 
direct  currents,  which  might  get  on  the  indication 
wire^  from  crosses  with  other  wires  or  grounds, 
giving  a  wrong  indication.  A  direct  current  of  uni- 
form pressure  passing  through  the  transformer  will 
have  no  noticeable  effect  on  the  indication  motor. 

The  high  signals  used  with  this  type  of  interlocking 
are  differently  constructed  from  any  yet  described, 
and  as  a  signal  constructed  on  the  same  principle  is 
used  for  many  other  purposes  connected  with  inter- 
locking and  block  signaling,  we  shall  take  space  to 
describe  it  fully. 

Fig  79  gives  a  view  of  the  mechanism  of  one  of 
of  these  signals  and  also  three  separate  views  of  the 
slot  arm  which  is  the  most  unique  part  thereof. 

It  will  be  noted  that  two  slot  arms  are  shown  in 
the  view  of  the  full  mechanism.  This  is  for  a  two 


196 


EAILWAY  SIGNALING 


arm  signal.  With  a  one  arm  signal  only  one  slot  arm 
is  necessary.  For  purposes  of  illustration,  it  is  con- 
venient, however,  to  show  one  arm  inclined  upward 


Fig.  79. 

and  one  downward  so  the  two  arm  mechanism  has 
been  used  in  the  illustration. 

M  is  the  motor  which  is  put  in  motion  when  the 


IN  THEORY  AND  PRACTICE. 


197 


leverman  reverses  the  lever  and  through  suitable  gear- 
ing revolves  the  sprocket  wheel  B.      This  winds  up 
I 


(ARUATURr  UNLATCHED.) 


Fig.  80. 


on  the  endless  chain  which  passes  around  it.  In  this 
endless  chain  is  a  pin  "b,"  which  engages  a  forked 
head  at  the  end  of  the  slot  arm  A.  C  is  the  pole 


198  SA1LWAY  SIGNALING 

changer  or  circuit  controller.  When  the  signal  is 
normal  this  pole  changer  connects  one  set  of  field 
coils  in  the  motor  in  series  with  the  coils  of  the  slot 
magnet,  so  that  the  slot  magnet  is  energised  and  the 
forked  head  of  the  slot  arm  is  held  rigid.  This  is 
easily  seen  by  reference  to  Fig.  80,  showing  the  slot 
arm  in  detail.  When  the  motor  revolves,  therefore, 
and  winds  up  the  chain,  it  raises  the  end  of  the  slot 
arm,  which  in  turn  pushes  up  on  the  up  and  down  rod 
and  clears  the  signal.  On  going  to  its  full  clear  posi- 
tion the  signal  shifts  the  pole  changer  so  as  to  cut 
current  off  the  motor  and  also  switch  it  through  a  high 
resistance  coil  of  the  slot  magnet.  Although  the  figure 
does  not  show  it,  it  should  be  understood  that  the  slot 
magnet  is  really  two  separate  pairs  of  magnets  wound 
about  the  same  cores.  That  in  series  with  the  motor  is 
low  resistance  so  as  not  to  reduce  the  amount  of  cur- 
rent going  to  the  motor  coils,  and  the  other,  through 
which,  as  just  stated,  the  current  is  switched  when  the 
signal  is  at  full  clear,  is  of  high  resistance  so  as  to  use 
up  a  minimum  of  current  while  the  signal  stays  at 
clear. 

The  signal  motor  like  the  switch  motor  has  two 
sets  of  field  coils,  one  to  make  it  revolve  in  one  direc- 
tion, the  other  to  reverse  that  movement.  When  the 
leverman  returns  the  lever  to  normal,  current  is  cut 
off  from  the  slot  arm  magnet,  its  armature  is  released, 
unhooking  the  latch  of  the  slot  arm,  which  in  turn 
releases  the  forked  head,  allowing  it  to  bend  back- 
ward as  illustrated  in  the  figure.  This  lets  that  end 
of  the  slot  arm  which  is  being  borne  down  by  the 
weight  of  the  up  and  down  rod  and  the  arm  plate, 
drop  down,  allowing  the  signal  to  return  to  normal. 
When  the  slot  arm  is  in  its  full  down  position  the 
forked  head  falls  forward  by  gravity,  thus  placing 
the  hook,  which  is  hinged  to  it,  over  the  armature 


IN  THEOEY  AND  PRACTICE. 


199 


of  the  slot  arm  magnet  in  such  a  way  that  as  soon 
as  that  magnet  is  again  energised  the  hook  will  hold 
the  forked  head  rigid. 

As  with  other  types  of  power  interlocking,  the  sig- 
nals indicate  from  the  normal  position  only. 

Current  for  the  signal  indication  is  generated  by 
a  transformer  in  exactly  the  same  manner  as  with  a 
switch  machine. 

An  air  dash  pot,  much  like  the  air  cushions  put  on 
doors,  prevent  the  signals  dropping  back  to  normal 
too  violently. 


Fig.  81. 

The  dwarf  signals  used  with  the  Union  Switch 
and  Signal  Company's  all  electric,  or  at  least  that 
type  of  it  now  under  discussion,  are  operated  by 
motors,  but  are  not  provided  with  a  slot  arm.  The 
motor  through  proper  gearing,  readily  understood 
from  Fig.  81,  which  shows  a  sectional  view  of  one 
of  these  signals,  shoves  the  arm  plate  to  clear  against 
the  action  of  a  coil  spring.  This  spring  acts  as  a 
counter  weight  to  restore  the  signal  to  normal.  The 


200  RAILWAY  SIGNALING 

arm  plate  is  held  in  the  clear  position  by  a  magnetic 
brake  of  high  resistance  through  which  the  battery 
current  is  switched  from  the  motor. 

In  addition  to  the  one  which  we  have  just  been 
describing,  the  Union  Switch  and  Signal  Company 
has  recently  put  out  an  all  electric  interlocking,  some 
parts  of  which,  more  especially  the  machine,  are  of 
an  entirely  different  design.  Although  this  is  of  a 
very  recent  appearance  and  may  yet  be  altered  in 
some  of  its  details,  we  will  say  a  few  words  about 
it  here.  The  levers  in  the  machine  are  arranged  to 
be  pulled  outward  and  then  pushed  downward  when 
being  reversed.  The  hand  hold  is  a  good  deal  like 
the  stock  of  a  pistol.  The  levers  operate  quadrants, 
and  the  feature  of  latch  locking  mechanically  applied 
is  a  part  of  their  operation.  Like  the  low  pressure 
pneumatic  these  machines  are  so  constructed  that  the 
stroke  of  the  lever  is  automatically  completed  by  re- 
lease of  the  indication.  This  by  the  way  is  a  feature 
which  may  be  applied  to  the  Union  Switch  and  Signal 
Company's  other  type  of  all  electric  machine,  al- 
though rarely  done.  The  indication  current  for 
switch  movements  and  high  signals  is  derived  in  a 
manner  exactly  similar  to  that  already  described  for 
this  Company's  other  type  of  all  electric  machine.  It 
is  stepped  up,  however,  from  110  to  220  volts  pres- 
sure. The  dwarf  signals  are  of  the  solenoid  type  and 
indicate  by  switching  the  battery  current  over,  much 
as  is  done  by  the  General  Railway  Signal  Company's 
dwarf  signals.  The  switch  levers  are  provided  with 
latch  circuit  breakers  to  be  used  in  connection  with 
detector  circuits,  a  discussion  of  which  we  are  reserv- 
ing for  a  later  chapter.  The  locking  is  of  the  vertical 
type.  The  switch  and  high  signal  movements  are 
in  all  essentials  identical  with  those  described  as  used 
with  this  company's  earlier  all  electric  interlocking. 


IN  THEORY  AND  PRACTICE. 


201 


Fig.    82. 


202  RAILWAY  SIGNALING 

The  dwarf  signals  are,  as  just  stated,  of  the  solenoid 
design. 

Fig.  82  gives  a  section  through  one  of  these  ma- 
chines, from  which  the  reader  will  easily  discern  the 
principle  points  of  difference  between  it  and  the  other 
types  we  have  met  with  so  far. 

The  Federal  Railway  Signal  Company's  all  electric 
interlocking  is  the  next  type  we  shall  consider. 

There  is  a  radical  difference  between  it  and  any  of 
the  foregoing,  with  respect  to  the  machine  used. 

The  Federal  machine  is  a  miniature  Saxby  and 
Farmer  machine  throughout  —  levers,  quadrants, 
latches  and  all,  and  the  feature  of  latch  locking  ap- 
pears in  this  machine  just  as  it  does  in  one  designed 
for  a  mechanical  plant. 

The  operating  contacts  are  made  much  as  they  are 
in  the  electro  pneumatic  or  Union  Switch  and  Signal 
Company's  all  electric  machines  of  the  vertical  roller 
type.  The  vertical  rollers  are  in  the  front  of  the 
machine  frame,  however,  and  two  good  strong  bus 
bars  are  placed  below  them. 

The  indication  magnets  are  fitted  into  a  cast  iron 
frame  so  that  it  is  impossible  to  reach  under  them 
and  push  up  the  armature  of  the  indication  magnet 
as  may  be  done  with  the  General  Railway  Signal  Com- 
pany's all  electric  machine,  if  the  glass  cover  of  the 
case  enclosing  the  locking  and  circuit  breakers  is 
removed. 

The  mechanical  operation  of  the  indication  magnet 
is  to  have  its  armature  when  the  magnet  is  energised 
bear  on  one  end  of  a  latch  in  such  a  way  that  the  other 
end  will  be  depressed.  This  latch  is  attached  to  a 
bar  which  is  in  turn  attached  to  the  lever  and  slides 
backward  and  forward  in  a  horizontal  plane  as  the 
lever  is  set  normal  or  reversed.  The  end  of  the  latch 
which  is  not  acted  on  by  the  armature  is  provided  with 
a  knob  or  dog  which,  when  the  magnet  is  de-energised 


IN  THEORY  AND  PRACTICE.  208 

and  the  armature  down,  engages  a  steel  bar  extending 
along  the  entire  front  of  the  machine,  under  and 
parallel  to  the  front  of  the  locking  bed.  The  reverse 
indication  acts  in  the  opposite  way. 

The  indication  magnets  are  energised  by  battery 
current. 

The  switch  movements  are  a  screw  arrangement 
operated  by  a  motor  somewhat  similar  in  general  prin- 
ciples to  those  furnished  with  the  Union  Switch 
and  Signal  Company's  all  electric  interlocking.  The 
screw  is  not  a  cam  but  a  regular  screw  and  its  outer 
end  is  attached  to  the  slide  bar  of  an  ordinary  switch 
and  lock  movement.  The  battery  current  is  switched 
from  the  motor  to  the  indication  circuit  by  a  pole 
changer,  mechanically  operated  by  the  movement  of 
the  switch  and  lock  movement.  The  motor  is 
stopped  by  a  magnetic  brake  and  its  shaft  is  held  to- 
gether by  a  magnetic  clutch  which  slips  in  case  some- 
thing prevents  the  switch  or  detector  bar  from  mov- 
ing when  current  is  sent  through  the  motor.  Fuses 
are  provided  in  the  machine  as  well. 

There  is  no  vital  difference  in  the  wiring  arrange- 
ment between  this  and  other  types  of  all  electric  inter- 
locking. At  the  present  writing  it  is  understood  that 
this  company  is  engaged  in  perfecting  another  de- 
sign of  switch  machine  and  is  also  contemplating  a 
change  in  its  method  of  generating  its  indication  cur- 
rent. 

The  signal  machines  are  simple,  a  motor  operating 
through  gearing  and  hold  clear  magnets  of  high  re- 
sistance to  hold  the  signal  after  the  motor  is  stopped. 
Both  home  and  dwarf  signals  depend  on  gravity  to 
restore  them  to  normal. 

The  American  Railway  Signal  Company's  machine 
is  so  constructed  that  the  levers  are  shafts  with  han- 
dles, something  like  those  of  the  General  Railway 
Signal  Company's  machine.  In  reversing  they  must 


204 


BAILWAY  SIGNALING 


first  be  given  a  sidewise  twist  and  then  pulled  out 
toward  the  leverman  where  they  are  stopped  at  the 
end  of  the  stroke  with  the  locking,  which  is  of  the  Sax- 
by  and  Farmer  type,  uncompleted  until  the  indication 
is  received.  The  effect  of  the  indication  is  to  give 
the  shaft  a  further  sidewise  twist,  thus  completing 
the  stroke  of  the  locking  bar.  In  the  return  to  nor- 
mal the  process  is  reversed.  Like  the  low  pressure 


Fig.  83. 

pneumatic  and  latest  type  of  all  electric  machine  of 
the  Union  Switch  and  Signal  Company,  the  indication 
completes  the  stroke  of  the  lever  automatically. 

The  indication  current  is  furnished  by  the  battery. 
The  indication  magnet  is  a  solenoid.  Circuit  through 
this  solenoid  is  broken  through  the  front  contact  of  a 
relay.  A  relay,  about  which  device  we  shall  hear 


IN  THEOEY  AND  PRACTICE.  205 

a  great  deal  further  on,  is  an  electric  magnet  whose 
armature  is  attached  to  a  small  lever  made  of  a  low 
resistance  material.  This  small  lever  is  hinged  at 
one  end  and  free  at  the  other  to  play  between  two 
bearings.  When  the  magnet  is  energized  so  as  to 
attract  its  armature  the  relay  is  said  to  be  "picked 
up."  When  the  magnet  is  de-energised  so  that  the 
armature,  which  is  always  underneath  the  magnets, 
has  fallen  away  from  the  end  of  the  cores,  it  is  said 
to  be  "down."  When  picked  up,  the  free  end  of  the 
lever  bears  against  one  of  the  bearings,  but  does  not 
touch  the  other.  This  bearing  is  called  the  front 
contact.  When  the  relay  is  down  the  lever  bears 
against  the  other  bearing,  called  the  back  contact, 
and  does  not  touch  the  front  contact. 

Fig.  83  shows  a  relay  diagrammatically,  with  the 
contact  points  indicated.  It  is  easily  seen  that  if  a 
wire  leading  from  one  pole  of  a  battery  is  attached  to 
the  hinge  of  the  lever  and  a  wire  leading  from  the 
other  pole  is  attached  to  the  front  contact  point, 
that  every  time  the  relay  is  picked  up  the  circuit  will 
be  closed  and  current  will  flow.  When  the  relay  is 
down  the  circuit  will  be  open.  As  before  stated  with 
the  interlocking  machines  we  are  now  discussing  the 
circuit  through  the  solenoid  is  broken  through  the 
front  contact  of  a  relay.  This  relay  is  normally 
down. 

The  current  to  pick  up  the  relay  is  furnished  by  an 
induction  coil.  This  is  an  arrangement  by  which  a 
coil  of  insulated  wire  is  wound  around  the  outside 
of  the  coil  of  an  electro  magnet.  Every  time  the  elec- 
tro magnet  is  energized  a  current  is  sent  out  from  the 
outside  coil  which  is  connected  with  the  relay.  By 
using  a  low  resistance  coil  for  the  electro  magnet, 
which  is  called  the  primary  coil,  and  a  coil  of  a  great 
many  turns  of  fine  wire  for  the  outside  coil,  which  is 
called  the  secondary  coil,  a  great  difference  in  the 


20«  EAILWAY  SIGNALING 

electric  pressure  in  the  operating  current  which  goes 
through  the  primary  coil  and  in  the  induced  current 
which  is  generated  in  the  secondary  coil,  is  effected. 
The  induction  coils  used  with  the  machine  under  dis- 
cussion send  a  current  of  5000  volts  pressure.  The  cir- 
cuit through  which  this  current  works  is  always  open, 
but  a  current  under  as  high  a  pressure  as  5000  volts 
will  jump  across  a  small  gap  such  as  is  left  in  the  cir- 
cuit, just  as  we  often  see  the  current  in  a  street  car 
trolley  wire  jump  across  to  the  trolley  pole  when  the 
latter,  after  having  slipped  off,  is  being  put  back  in 
place  by  the  conductor  of  the  car,  and  before  the  two 
have  come  together  so  as  to  make  a  perfect  contact. 

As  this  high  pressure  current  is  only  in  use 
momentarily  and  the  parts  of  the  machine  through 
which  it  passes  are  well  protected^  its  use  is  not  con- 
sidered dangerous. 

The  presence  of  this  gap  prevents  any  low  pres- 
sure currents  which  may  get  on  the  indication  wires 
by  crosses  or  from  other  causes  from  going  through 
the  relay  and  picking  it  up  at  the  wrong  time,  as  they 
have  not  force  enough  to  jump  the  gap.  The  indica- 
tion coil  is  placed  in  a  neat  cast  iron  box  near  the 
switch  movement. 

The  switch  movement  itself  consists  of  a  110  volt 
motor  which  drives  a  shaft.  This  shaft  has  a  pinion 
keyed  to  it  about  half  way  between  the  motor  and 
the  end  of  the  shaft  farthest  away  from  the  motor. 
This  pinion  engages  a  rack  working  at  right  angles 
to  the  shaft.  This  rack  is  attached  to  the  head  rod 
of  the  switch  by  an  ordinary  special  switch  adjust- 
ment. A  cam  screw  is  attached  to  the  end  of  the  shaft 
farthest  from  the  motor  which  operates  the  detector 
bar  and  lock.  A  circuit  shifter  or  pole  changer  is 
also  operated  by  the  lock  movement  which  switches 
the  battery  current  through  the  primary  coil  of  the 
induction  coil  when  the  switch  is  over  and  locked. 


IN  THEORY  AND  PRACTICE.  207 

The  high  signal  motors  are  arranged  to  wind  up  a 
chain  which  is  attached  through  a  bronze  rod  to- a  seg- 
ment to  which  the  spindle  of  the  arm  plate  is  keyed. 
The  signals  are,  therefore,  pulled  to  clear.  The  arm 
plates  are  very  heavy  and  act  as  a  counterweight  to 
restore  the  blades  to  normal.  The  dwarf  signal  mech- 
anisms are  much  the  same  as  those  of  the  high  signal. 
As  this  company  manufactures  an  automatic  block 
signal  on  exactly  similar  lines  to  its  interlocking  signal 
we  will  reserve  a  more  detailed  description  for  a  later 
page. 

The  reader  may  perhaps  wonder  by  this  time  why 
there  are  so  many  different  designs  of  power  inter- 
locking in  use,  all  aimed  to  accomplish  the  same  end, 
namely,  to  throw  and  lock  switches  and  movable 
frogs  and  to  throw  signal  blades. 

There  is  only  one  answer  to  such  a  thought.  Power 
interlocking  having  become  a  practical  possibility  com- 
paratively recently,  the  patents  on  the  various  appar- 
atus used  still  hold.  Each  manufacture  is  desirous  of 
being  able  to  furnish  the  railroads  with  all  sorts  of 
interlocking  and  signaling  devices.  As  certain 
patents  are  held  by  each  manufacturer  to  the  ex- 
clusion of  the  others,  each  has  been  forced  to  de- 
velop power  interlocking  machinery  of  his  own. 

No  doubt  when  power  interlocking  has  reached  the 
same  condition  in  which  mechanical  interlocking  is 
found  today,  where  any  manufacturer  may  build 
apparatus  in  all  important  particulars  exactly  similar 
to  that  built  by  the  others,  the  Railway  Signal  Asso- 
ciation will  narrow  its  specifications  for  power  inter- 
locking to  a  point  where  but  one  style  of  apparatus 
will  be  manufactured  by  all  makers.  The  power 
plant  of  the  future  will  no  doubt  embody  the  best 
features  of  the  several  designs  now  used,  with  the 
addition  of  such  improvements  as  will  from  time  to 
time  suggest  themselves.  To  a  certain  extent  it  is 


208  EAILWAY  SIGNALING 

a  pity  that  some  of  the  energy  now  being  expended 
in  developing  new  types  of  power  interlocking  can- 
not be  applied  to  improving  designs  already  in  use. 

At  present,  and  for  some  time  to  come  the  signal 
engineer  must  face  conditions  as  they  exist  and  must 
use  his  best  judgment  in  selecting  the  type  of  appar- 
atus best  suited  to  his  needs. 

Any  one  of  the  six  designs  described  will  do  the 
work  required  of  it,  if  well  installed  in  a  satisfactory 
manner. 

From  the  signal  engineer's  standpoint  it  is  always 
objectionable  to  have  too  many  designs  of  apparatus 
under  his  supervision,  as  it  requires  the  carrying  in 
stock  of  a  much  greater  quantity  of  repair  parts  than 
would  be  the  case  if  only  one  type  was  used. 

A  zealous  critic  may  easily  find  fault  with  any 
system  yet  invented,  nor  is  it  likely  that  an  absolutely 
perfect  apparatus  will  ever  be  designed. 

The  electro  pneumatic  has  done  good  work  for 
many  years,  but  the  cost  of  supplying  compressed  air 
where  a  source  of  supply  is  not  already  provided 
makes  it  very  expensive  to  operate. 

The  facility  with  which  the  indication  magnets  may 
be  tampered  with  in  the  General  Railway  Signal 
Company's  all  electric  is  objected  to  by  some  critics, 
and  so  on  through  the  list. 

Power  interlocking  has  a  large  field  of  usefulness, 
but  it  is  not  likely  that  for  many  years  to  come  it  will 
entirely  supplant  the  mechanical  apparatus. 

A  very  good  rule  to  follow  is  never  to  use  a  power 
plant  where  a  mechanical  plant  will  do  the  work. 
That  is,  if  all  the  switches  to  be  operated  are  within 
a  radius  of  seven  hundred  feet  from  some  central 
point  where  the  tower  may  be  conveniently  placed, 
and  the  traffic  conditions  are  such  that  the  levers  do 
not  have  to  be  moved  so  frequently  that  the  physical 
strain  on  the  leverman  becomes  so  great  that  frequent 


IN  THEOEY  AND  PRACTICE.  209 

shifts  of  men  are  required,  a  mechanical  plant  will,  in 
most  cases  be  found  much  more  economical  to  main- 
tain and  fully  as  satisfactory  to  operate. 

It  will,  even  as  a  general  thing,  pay  to  spend  con- 
siderable money  in  rearranging  tracks  and  switches 
so  as  to  bring  them  within  the  reach  of  a  mechanical 
plant,  where  the  traffic  conditions  will  warrant  using 
one. 

The  introduction  of  power  interlocking  has  de- 
veloped a  tendency  to  attempt  to  extend  the  limits  of 
interlocking  plants  so  far  that  it  becomes  impossible 
for  a  leverman  to  control  train  movements  as  he 
should,  and  in  that  respect  has  sometimes  over-reached 
itself,  even  to  the  point  of  occasioning  serious  delays 
in  the  movement  of  trains. 

After  a  few  general  remarks  on  the  installation  of 
power  interlocking  we  will  take  up  the  subject  of  ar- 
ranging interlocking  for  specific  cases,  and  the  prepar- 
ation in  connection  therewith  of  locking  and  dog 
charts. 

In  all  power  interlocking  the  wire  used  should  be 
copper.  That  which  is  to  be  placed  in  trunking  or 
any  other  conduit  should  be  either  in  the  form  of  a 
cable  or  the  wires  should  be  insulated  with  a  rubber 
preparation  over  which  one  or  two  thicknesses  of 
braid  should  be  wound.  Some  signal  engineers  in- 
sist on  a  coating  of  the  rubber  preparation  5-64  of  an 
inch  in  thickness;  others  are  satisfied  with  3-64  of 
an  inch.  Lead  covered  cables  are  not  to  be  recom- 
mended. 

There  is  room  for  a  good  conduit  which  is  not 
easily  broken,  may  be  kept  above  ground  and  affords 
easy  means  of  opening  it  up  to  take  the  place  of  the 
wooden  trunking  usually  used,  but  no  satisfactory 
substitute  has  yet  been  brought  out. 

Care  should  be  taken  to  avoid  jointing  wires  inside 
of  conduit.  Junction  boxes  which,  as  already  men- 


210 


HAILWAY  SIGNALING 


tioned,  are  small  terminal  boards  provided  with  bind- 
ing posts  may  be  used  very  conveniently  wherever 
wires  are  led  from  the  main  line  to  a  switch  or 
signal. 


SWITCH  L£i/£#7^ 

Contact  dosed  when  Lever  is  normaf. 
Contact  closed  when  Lever  15  reversed 


of  Lever. 

Contact  c  . 

until  it  has  ust  assed  center. 


. 

Contact  closed  when  Lever  is 
until  it  has  u 


FI6.I 


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until  it  has  just  passed  center  EB-F/G.1. 
LEVER. 


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Closed  at  A.  bet.  AandB,  andatd.  C- Middle  or  Normal 

iafD.  D'&oaf Quadrat Jfyfoftgh, 


Standard  Dwarf  Ind.  Brush 

M      H- 


111  MJ- 

^~5peaab-^ 

HH      MW 


Fixed  fostfaixe. 


I  Lever  Control 


High  3ig.  with  extra 
normal  contact    \ 

W"    H 

n 


Switch  with  etfru 


fix 


www 
flfln 


JL      JL  injer 

$\ Magneto.      v~x          Q&nerator  A.  Mf 

191  Motor-Generator  ^  y  Motor. 


BatteryCe/b     Batten/Cells 
in  Series        ID  Multiple 


Fig.  84. 


Wherever  wires  are  joined  the  two  ends  should  be 
wrapped  around  each  other  tightly,  and  should  then 
be  thoroughly  soldered,  after  which  the  joint  should 
be  well  wrapped  with  adhesive  tape  covered  with 
cotton  braid  tape.  Care  should  always  be  taken  to 


IN  TEEOEY  AND  PEACTICE.  211 

cut  off  the  outer  braid  from  the  wire,  leaving  the 
rubber  insulation  exposed  for  from  half  an  inch  to 
one  inch  on  either  side  of  the  joint.  This  will  allow 
the  adhesive  tape  to  take  hold  of  the  rubber  covering 
of  the  wire,  which  makes  a  much  tighter  joint  than 
if  the  braid  is  allowed  to  get  under  the  adhesive  tape. 
Care  should  be  taken  to  get  all  wires  large  enough. 
Tables  are  to  be  had  showing  the  size  wire  Brown  and 
Sharpe  gauge  to  be  used  for  currents  at  different 
pressures  and  different  distances.  At  interlocking 
plants  it  is  well  to  stand  on  the  safe  side  and  use 
wire  a  size  or  two  larger  than  the  tables  call  for. 

There  are  so  many  good  storage  batteries  and  gen- 
erators on  the  market  that  very  little  need  be  said  on 
that  head,  except  that  the  battery  should  be  of  large 
enough  capacity  to  run  ten  days  on  one  charge  if 
possible. 

Fig.  84  is  a  table  of  the  conventional  signs  used 
on  drawings  to  denote  the  different  apparatus  used 
with  power  interlocking. 


CHAPTER  XVI. 

LOCKING  AND  DOG   SHEETS. 

After  it  is  decided  to  build  an  interlocking  plant, 
at  a  given  point  on  a  railroad,  and  the  track  plan, 
described  in  an  earlier  chapter,  has  been  prepared, 
it  becomes  necessary  to  prepare  other  plans  from 
which  the  mechanics  who  build  the  interlocking  ma- 
chines can  work  in  order  to  have  the  proper  locking 
in  the  machine.  The  first  step  is  to  draw  up  a  list 
of  the  necessary  locking  for  each  lever  to  perform. 
This  is  called  the  locking  sheet  or  locking  chart.  It 
is  simply  a  list  of  the  levers  in  the  machine,  showing 
what  locking  each  accomplishes  when  it  is  reversed. 
For  instance,  the  locking  sheet  of  an  eight  lever  in- 
terlocking machine  might  read  as  follows : 

Lever  No.  i  when  reversed  locks  Lever  No.  2, 
reversed. 

Lever  No.  2  when  reversed  locks  Lever  No.  3, 
reversed,  and  No.  7  normal. 

Lever  No.  3  when  reversed  locks  Lever  No.  4, 
normal. 

Lever  No.  4  when  reversed  locks (see  note). 

Lever  No.  5  when  reversed  locks  Lever  No.  4, 
reversed,  and  No.  6,  normal. 

Lever  No.  6  when  reversed  locks  Lever  No.  4, 
reversed  (see  note). 

Lever  No.  7  when  reversed  locks  Lever  No.  3, 
reversed  (see  note). 

Lever  No.  8  when  reversed  locks  Lever  No.  7  re- 
versed (see  note). 

In  practice  conventional  signs  are  used  as  sub- 
stitutes for  a  great  many  of  the  words  in  the  above 

212 


IN  THEOEY  AND  PEACTICE. 


213 


description.  Locking  sheets  are  ruled  in  two  col- 
umns, in  the  first  of  which  the  numbers  of  the  levers 
are  given  in  numerical  order,  and  in  the  second,  fol- 
lowing the  numbers  in  the  first,  are  the  numbers  of 
the  levers  which  they  lock.  Nothing  is  said  about  the 
levers  whose  numbers  are  given  in  the  first  column 
being  reversed,  but  it  is  always  understood  that  they 
must  be  reversed  to  accomplish  the  locking  which 
is  shown  in  the  second  column.  Instead  of  writing 
in  the  word  "reversed"  in  the  second  column,  a  circle 
is  drawn  around  the  number  denoting  a  lever  when 
that  lever  is  locked  reversed. 

The  locking  sheet  described  above  would  in  prac- 
tice appear  as  follows: 


LEVER 

LOCKS 

1 

© 

2 

© 

7 

3 

4 

4 

5EE  NOTE 

5 

C43 

6 

6 

(4)                  5£F  NOTE 

7 

(3) 

SEE  NOTE 

8 

(7) 

Fig.  85. 

Note. — As  explained  in  an  earlier  chapter,  if  one  lever 
locks  another  lever  normal,  the  opposite  is  always  true, 
i.e.,  the  last  lever  locks  the  first  normal.  In  the  locking 
sheet  illustrated  No.  3  locks  No.  4  normal.  No.  5  locks  No. 
6  normal;  No.  2  locks  No.  7  normal;  therefore  No.  4  locks 
No.  3  normal;  No.  6  locks  No.  5  normal;  No.  7  locks  No.  2 
normal.  It  is  not  customary  to  show  this  duplication  in 
drawing  off  locking  sheets,  and  as  illustrated,  no  mention  is 
made  in  the  locking  given  for  the  last  named  levers  of  the 
fact  that  they  lock  the  first  named  normal. 

This  is  merely  a  conventionality  and  no  harm  would  be 


214 


EAILWAY  SIGNALING 


done  if  it  was  shown,  but  as  the  established  custom  is  to 
omit  it  this  custom  had  better  be  followed. 

Where   special   locking  appears,   the   letter   "w"   is 
placed  in  the  second  column  between  the  number  of 


\\LEVER 

LOCKS                            1 

i 

5 

W 

(7)                           1 

Fig.  86. 


a  lever  which  is  locked,  and  the  number  of  the  lever 
or  levers  which  must  be  in  an  assigned  position  be- 
fore that  locking  is  accomplished.  To  illustrate : 

Fig.  86  would  indicate  that  lever  No.   I  when  re- 
versed locks  lever  No.  5  normal,  when  lever  No.  7  is 


\LEVER 


LOCKS 


II    /    " 

<6)       IV 

C8) 

5                | 

Fig.  87. 

reversed,  and  Fig.  87  would  indicate  that  lever  No.  I 
when  reversed  locks  lever  No.  6  reversed  when  lever 
No.  8  is  reversed  and  lever  No.  5  is  normal. 

In  large  machines  where  some  levers  lock  a  great 
many  others,  and  where  if  the  special  locking  was 
shown  on  the  same  line  with  the  straight  locking  it 
might  be  confusing  to  distinguish  the  special  from 
the  straight,  it  is  customary  to  show  all  the  straight 
locking  on  one  or  more  lines,  together,*  and  each 
special  combination  on  a  line  by  itself. 

For  example :     Fig.  88 


LEVER 

LOCKS 

63 

(5)      ?8      32 

44      (22) 

*-fr*r            \r*j7 

it     w    n 

Q$       W        ?9      d§) 

Fig.  88. 


IN  THEORY  AND  PRACTICE.  215 

would  indicate  that  lever  No.  23  when  reversed 
would  lock  lever  No.  5  reversed,  levers  Nos.  28  and 
32  normal,  lever  No.  44  normal  and  reversed,  lever 
No.  11  normal,  when  lever  No.  27  was  reversed,  lever 
No.  36  reversed,  when  lever  No.  29  was  normal  and 
lever  No.  16  was  reversed. 

The  method  of  describing  locking  on  locking  sheets 
just  explained  is  that  used  by  many,  but  it  is  only 
proper  to  add  here  that  one  large  manufacturing  com- 
pany draws  up  its  locking  sheets  in  a  different  form. 
Its  method  is  to  rule  the  sheets  in  three  columns  as 
Fig.  89. 


LEVER 

WHEN 

LOCKS 

?d 

(5)     m     32 

44      @ 

(?7) 

// 

©       29 

® 

Fig.  89. 

The  locking  given  is  the  same  as  that  just  described 
and  means  that  lever  23  when  reversed  locks  lever  5 
reversed  levers  28  and  and  32  normal  and  lever  44 
normal  and  reversed;  that  when  lever  27  is  reversed 
it  (lever  23)  locks  lever  11  normal  and  that  when 
lever  16  is  reversed  and  lever  29  normal  it  (lever  23) 
locks  lever  36  reversed. 

There  are  some  advantages  in  drawing  off  locking 
this  way  as  the  specials  can  be  put  in  the  "when" 
column  first  and  act  as  a  check  to  the  draftsman  when 
completing  his  sheet. 

However,  the  former  method  is  that  most  generally 
employed  and  will  be  used  throughout  this  work. 

Dog  sheets  are  neither  more  nor  less  than  plan  views 
of  the  locking  beds  of  machines  with  all  parts  omitted 
except  the  dogs,  locking  bars,  cross  locks  and  drivers, 
with  Saxby  and  Farmer  machines,  and  dogs,  tappets 
and  locking  bars  in  vertical  locking  machines. 

Dog  sheets  for  Saxby  and  Farmer  machines  are  al- 


216  RAILWAY  SIGNALING 

ways  shown  with  the  front  of  the  locking  bed  at  the 
top  of  the  drawing.  This  gives  the  view  of  the  lock- 
ing bed  as  if  the  observer  was  standing  behind  the 
machine,  and  consequently  No.  1  lever  is  at  the  right 
and  all  locking  bars  in  mechanical  machines  move 
towards  the  right  of  the  drawing.  As  explained  ear- 
lier, in  some  types  of  power  machines  with  Saxby  and 
Farmer  locking,  some  levers  drive  the  bars  both  ways. 
Dog  sheets  for  vertical  locking  beds  show  the  tappets 
and  dogs  as  they  would  appear  to  an  observer  stand- 
ing with  No.  1  lever  at  his  left.  As  the  direction  in 
which  the  locking  bars  in  these  machines  move  is  gov- 
erned by  the  position  of  the  notches  in  the  tappets, 
with  respect  to  the  side  of  the  tappet,  it  makes  no 
difference  whether  the  tappets  are  raised  or  lowered 
by  the  movement  of  the  lever  or  its  latch.  In  the  case 
where  one  lever  locks  another  reversed,  the  direction 
in  which  the  tappets  move  does,  of  course,  have  some 
bearing,  but  as  in  that  case  the  first  lever  cannot  be 
reversed  until  the  second  has  been  reversed,  the  po- 
sition of  the  notch  in  the  second  lever  shows  at  a 
glance  in  which  direction  the  tappets  must  move. 

Fig.  90  shows  a  dog  sheet  for  a  Saxby  and  Farmer 
machine,  and  Fig.  91  one  for  a  vertical  locking  ma- 
chine, in  which  the  tappets  move  upward,  and  one  for 
a  vertical  locking  machine,  in  which  they  move  down- 
ward, each  of  which  accomplished  the  locking  shown 
in  the  locking  sheet  first  described  in  this  chapter. 

There  is  no  fixed  mathematical  method  by  which 
the  proper  locking  to  be  shown  on  locking  sheets  or 
the  proper  distribution  of  the  dogs  on  dog  sheets,  may 
be  calculated. 

There  are  a  few  general  rules  which  must  be  ob- 
served, after  which  the  question  becomes  merely  a 
matter  of  skill  and  practice,  like  the  playing  of  a 
game  of  chess  or  checkers.  In  fact,  two  experts 


IN  THEORY  AND  PRACTICE. 
6       7      6      5       4      3      2       / 


3 
4 

5 
6 

7 
6 

9 
10- 


217 


-6 

•9 

•K) 


218  RAILWAY  SIGNALING 

working  on  the  same  track  plan,  may,  and  frequently 
do,  design  different  locking  and  dog  sheets,  either  of 
which  will  accomplish  the  desired  results.  There  is 
probably  no  one  thing  in  signal  engineering  that  re- 
quires as  much  mental  concentration  as  the  designing 
of  locking.  From  three  to  five  years'  constant  prac- 
tice is  considered  necessary  to  oroduce  a  skilled  lock- 
ing expert. 

The  vast  majoritv  of  the  dog  sheets  are  made  up 
in  the  drafting  rooms  of  the  signal  manufacturers, 
few  signal  engineers  deeming  it  worth  while  to  un- 
dertake their  preparation  in  their  own  offices.  A  great 
many  locking  sheets,  too,  are  prepared  by  the  manu- 
facturers from  track  plans,  and  a  general  description 
of  the  traffic  conditions  furnished  by  the  signal  en- 
gineer, although  many  signal  engineers  who  do  not 
care  to  prepare  their  own  dog  sheets,  do  prepare  and 
furnish  locking  sheets. 

The  manufacturers  always  insist  on  having  a  writ- 
ten acceptance  of  the  locking  in  each  machine,  from 
the  Railroad  Company  purchasing  it,  in  order  to  clear 
themselves  in  case  routes  are  not  properly  safeguarded 
by  the  locking.  Every  signal  man  should,  therefore, 
be  prepared  to  check  locking  and  dog  sheets  after 
they  have  been  drawn  up,  in  order  to  thoroughly  un- 
derstand the  various  locking  combinations  they  effect, 
and  so  detect  any  errors  which  may  have  slipped  by 
the  original  designer. 

As  a  matter  of  practice,  too,  it  is  always  a  good 
plan  to  draw  up  locking  sheets,  to  design  changes  in 
the  locking  of  machines  already  in  service  in  which 
additions  or  alterations  are  to  be  made,  and  even  to 
prepare  dog  sheets  for  small  machines.  It  is  very 
doubtful,  however,  if  it  ever  pays  a  railroad  company 
to  have  its  men  spend  much  time  in  designing  large 
dog  sheets.  In  the  nature  of  things  the  skilled  corps 
of  specialists  kept  by  the  manufacturers  are  in  a  bet- 


IN  THEOKY  AND  PEACTICE.  219 

ter  position  to  prepare  them,  especially  as  they  are  in 
close  touch  with  the  factory  where  the  locking  is  to 
be  made,  than  a  railroad  company's  man  who  cannot 
devote  his  entire  time  and  thought  to  this  one  branch 
of  the  art. 

This  is  more  especially  true  as  the  signal  companies 
make  no  extra  charge  for  machines,  the  dog  sheets 
for  which  they  themselves  have  prepared. 

The  following  general  rules  apply  to  all  locking 
sheets : 

1.  Each  distant  signal  lever  should  always  lock  its 
home  signal  lever  reversed.    As  before  explained,  this 
insures  that  the  home  signal  lever  must  be  reversed, 
before  the  distant  signal  lever  can  be  reversed,  or,  in 
other  words,  the  distant  signal  cannot  be  cleared,  un- 
less the  home  signal  has  first  been  cleared. 

2.  Facing  point  lock  levers  should  always  lock  the 
levers  of  the  switches  which  the  facing  point  locks 
secure  normal  and  reversed.     The  reason  for  this  is 
explained  as  follows :    The  plunger  of  a  facing  point 
lock  is  passed  through  the  lock  rod  of  the  switch  or 
derail  when  the  facing  point  lock  lever  is  reversed. 
Now,  if,  when  the  facing  point  lock  lever  is  reversed, 
the  lever-man  is  free  to  unlatch  and  move  the  switch 
lever,  he  will  throw  a  shearing  strain  on  the  plunger 
which  might  break  it  or  the  lock  rod.     By  having  the 
switch   lever   locked,   either   normal   or   reversed,   by 
the  lock  lever,  this  is  prevented. 

3.  Where  switch  and  lock  movements  are  used  the 
signal  lever  operating  each  signal  that  governs  any 
route  over  the  switch,  should  lock  the  switch  and  lock 
lever  normal,  if  the  switch  is  to  be  in  its  normal  posi- 
tion when  the  signal  is  clear,  or  reversed,  if  the  signal 
governs  a  route  over  the  switch  in  its  reversed  posi- 
tion. 

In  the  case  of  derails,  as  there  is  no  route  over  them 


220 


RAILWAY  SIGNALING 


in  their  normal  position,  the  signal  lever  should  lock 
the  switch  and  lock  lever  reversed. 

4.  Where  facing  point  locks  are  used,  the  lever  of 
each  signal  governing  a  route  over  any  switch  locked 
by  a  facing  point  lock  should  lock  the  facing  point 
lock  lever  reversed.  This  insures  that  the  switch 


4 


®J 


3&L 


S.&L 


Fig.  92. 

points  are  locked  by  the  facing  point  lock  plunger  be- 
fore the  signal  can  be  cleared.  This  also  applies  to 
derails. 

There  are  three  elementary  components  to  which, 
like  the  prime  factors  of  a  number,  all  interlocking 
may  be  reduced. 


IN  THEORY  AND  PRACTICE. 


221 


Each    interlocking   plant   is   made    up   of   one   or 
more  of  these  elements. 
They  are : 

(1)  A  plain  crossing. 

(2)  A  junction. 

(3)  A  crossover  between  two  tracks. 


Fig.  93. 


The  correct  signalling  for  a  plain  single  track  cross- 
ing is  shown  in  Fig.  92,  in  which  I,  2,  n  and  12  are 


222  EAILWAY  SIGNALING 

the  distant  signals,  3,  6,  8  and  10  the  home  signals, 
and  4,  5,  7  and  9  the  derails  shown  in  the  figure  as 
operated  by  switch  and  lock  movements. 

Where  one  of  the  lines  is  a  double  and  the  other 
a  single  track  line  the  signaling  is  shown  in  Fig.  93. 
This  is  merely  an  evolution  from  the  other. 

The  direction  of  traffic  on  the  double  track  line 
is  shown  by  the  arrows.  It  is,  as  explained  in  an 


Fig.  94. 

earlier  chapter,  customary  to  signal  reverse  move- 
ments, i.  e.,  those  opposite  to  the  established  direc- 
tion of  traffic,  with  dwarf  signals,  and  no  distant 
signals  are  provided  for  these,  hence  signals  1  and 
12  are  dwarf  signals. 

Where  both  lines  are  double  track,  we  have  a 
further  evolution,  as  shown  in  Fig.  94. 

In  order  to  prepare  the  locking  for  the  arrange- 


IN  THEOEY  AND  PRACTICE.  223 

ment  shown  in  Fig.  92  the  reader  should  remember 
that  in  the  plan  everything  is  shown  in  its  normal 
position ;  that  is,  the  derails  are  open  and  the  signals 
are  at  "caution"  for  the  distant,  and  "stop"  for  the 
home.  In  order  to  let  a  train  pass  from  A  to  B, 
therefore,  derails  4  and  7  and  home  signal  3  must 
be  reversed,  and  distant  signal  1  if  the  train  is  ap- 
proaching from  beyond  it  should  also  be  reversed. 

Further  than  this:  It  is  a  cardinal  principle  of 
all  interlocking,  that  a  route  given  to  a  train  must 
insure  that  train  a  safe  passage  through  the  inter- 
locking limits,  so  far  as  the  interlocking  is  con- 
cerned. Therefore,  when  derails  4  and  7  are  re- 
versed, derails  5  and  9  must  be  held  normal,  so  that 
any  train  approaching  on  the  other  line  C-D  would 
be  run  off  the  track  and  prevented  from  running 
into  the  train  which  had  been  given  the  right  of 
way.  As  it  would  be  highly  dangerous  and  only 
inviting  disaster  to  give  a  clear  signal  with  a  derail 
in  the  route  it  governs  normal,  all  signals  on  the 
line  C-D  must  also  be  normal. 

It  is  not  of  such  vital  importance  that  signals 
8  and  11  should  be  held  at  normal  because  if  a  train 
was  approaching  from  B  towards  A  at  the  time  a 
train  moving  from  A  towards  B  was  given  the 
route,  the  fact  that  signals  8  and  11  were  at  normal 
would  not  prevent  a  collision  between  the  trains. 
It  is  nevertheless  the  general  practice  to  arrange 
the  locking-  so  that  when  3  is  clear  8  must  be  nor- 
mal, and  vice  versa. 

In  order  then  to  insure  the  safeguards  just  de- 
scribed, derail  levers  4  and  7  should  each  lock  derail 
levers  5  and  9  normal.  As  before  explained,  this  car- 
ries with  it  that  5  and  9  will  lock  4  and  7  normal, 
so  that  when  either  derail  in  either  line  is  reversed, 
both  derails  in  the  conflicting  line  must  be  normal. 


224 


EAILWAY  SIGNALING 


In  order  that  signals  6  or  10  may  not  be  cleared 
while  route  is  given  from  A  to  B,  we  have  lever 
6  locks  levers  5  and  9  reversed,  also  lever  10  locks 
levers  5  and  9  reversed.  As  before  explained,  this 
locking  prevents  lever  6  or  10  from  being  reversed 
until  after  5  and  9  have  been  reversed,  and  as  5  and 
9  are  locked  normal  by^and  7,  neither  6  nor  10 
can  be  cleared  while  ^or  7  is  reversed.  The  distant 
signals  all  lock  their  home  signals  reversed,  so  that 
only  that  distant  signal  can  be  cleared  whose  home 
signal  is  first  set  clear.  Lever  3  should  lock  lever  8 
normal,  and  lever  6  should  lock  lever  10  normal,  to 
prevent  the  clearing  of  opposing  signals  on  the  same 
route,  which,  as  just  explained,  is  not  vital,  but  is 
considered  good  practice. 

The  locking  sheet  for  this  machine  then  would 
read  as  follows : 


LEVER 

LOCKS 

1 

3} 

2 

® 

3 

® 

(7) 

8 

4 

5 

9 

5 

6 

(5) 

(9) 

10 

7 

5 

9 

8 

(4) 

(7) 

9 

10 

qo 

(9) 

II 

® 

12 

© 

Fig.  S5. 


IN  THEORY  AND  PRACTICE. 


225 


It  is  very  common  practice  to  operate  both  de- 
rails in  one  line  at  a  crossing  by  one  lever,  and  to 
lock  them  with  facing  point  locks  thrown  by  an- 
other lever. 

Such  an  arrangement  is  shown  in  Fig.  96. 


F.PL. 


&F.P.L 


Fig.  96. 

Here  the  locking  would  be  as  shown  in  Fig.  97. 

In  the  cases  of  the  double  track  line  crossing  the 
single  track  and  of  the  two  double  track  lines 
crossing  each  other,  there  is  no  essential  differ- 
ence. There  need,  of  course,  be  no  locking  be- 
tween the  derails  and  signals  on  the  parallel  lines 
of  the  double  track  because  they  do  not  conflict  in 
any  way. 


226 


EAILWAY  SIGNALING 


Fig.  98  shows  a  junction  interlocked  and  the  lock- 
ing sheet  therefor. 

Here  it  should  be  noted  that  4  does  not  lock  5 
normal,  directly.  No.  5  locks  8  normal,  however, 
and  as  4  locks  8  reversed  4  cannot  be  reversed  un- 
til 8  has  been  reversed,  which  locks  5  normal. 

If  facing  point  locks  were  used  it  would  be  good 
practice  to  operate  derail  shown  as  No.  6  and 


LEVER 

LOCKS 

1 

55 

2 

(6) 

3 

(5) 

10 

4 

7 

5 

(4) 

6 

(8) 

9 

7 

8 

(7) 

9 

(8) 

10 

C5) 

II 

(sj 

l£ 

<w> 

Fig.  97. 

switch  No.  5  by  one  lever  and  lock  them  by  another. 
It  would  never  be  desirable  to  reverse  No.  6  with- 
out No.  5,  so  that  no  complication  could  arise  from 
working  them  both  together. 

Fig.  99  shows  such  an  arrangement  in  which 
lever  No.  5  throws  the  switch  and  derail  and  lever 
No.  6  throws  both  locks  and  bars.  No.  8  is  still 
left  a  switch  and  lock  movement.  If  it,  too,  is  to  be 


IN  THEORY  AND  PRACTICE. 


227 


©©  ®@ 


S.&L 


LEVER 

LOCKS 

1 

© 

2 

@ 

3 

(6)(D  7 

4 

(o)  5" 

9 

5 

f  ! 

6 

© 

7 

© 

8 

5 

9 

@ 

10 

m 

II 

G9) 

Fig.  98. 


Ftg.  99. 


228 


RAILWAY  SIGNALING 


LEVER 

LOCKS 

1 

55 

2. 

® 

3 

© 

®       7 

4 

(6) 

®       9 

5 

8 

6 

5 

(5) 

7 

®      © 

8 

9 

8 

(6) 

10 

CD 

11 

(93 

Fig.  100. 


Fig.  101. 

equipped  with  a  facing  point  lock  an  additional 
lever  will  have  to  be  added  for  the  lock. 

The  locking  sheet  for  Fig.  99  is  shown  in  Fig.  100. 

The  only  other  case  of  a  junction  which  can  come 
up  without  introducing  either  a  crossing  or  a  cross- 
over,  is  that  in  which  a  double  track  line  joins  a 
single  track  line,  and  is  shown  in  Fig.  101. 

The  direction  of  traffic  on  the  double  track  line  is 
indicated  by  the  arrows.  There  is  so  little  differ- 


IN  THEOEY  AND  PRACTICE. 


229 


ence  between  this  and  the  single  line  junction  that 
I  shall  not  take  space  here  to  give  the  locking. 
The  reader  no  doubt  can  by  this  time  make  a  lock- 
ing sheet  for  this  figure  himself. 

Crossovers  may  be  either  facing  point  or  trailing 
point.  There  is  a  slight  difference  in  the  signaling 
for  a  trailing  point  from  that  for  a  facing  point. 

Fig.  103  shows  one  of  each,  with  its  proper  sig- 
naling. A  crossover  is  very  nearly  akin  to  a  June- 


LEVER 

LOCKS 

1 

(4) 

2 

(5)       8 

3 

CD      /o 

4 

(§)      ll 

5 

6 

6 

7 

C6) 

8 

(5) 

9 

6 

10 

(7) 

II 

C9) 

12 

(8) 

Fig.  102. 

tion,  but  the  reader  will  no  doubt  notice  the  differ- 
ence in  the  arrangement  of  derails;  one  end  of  the 
crossover  itself  takes  the  place  of  one  of  the  de- 
rails at  a  junction,  but  another  derail  has  to  be 
added  to  protect  anything  using  the  crossover  from 
a  false  move  which  could  not  be  made  at  a  junc- 
tion. 

The  locking  sheet  for  the  facing  point  crossover 
would  be  as  shown  in  Fig.  102. 


230 


RAILWAY  SIGNALING 


© 


-LEVER 

LOCKS 

1 

(2) 

2 

(<3)       7 

.3 

5 

6 

4 

5       © 

(8) 

W 

5 

9 

W 

5 

<§) 

W 

@ 

7 

W 

C53 

5 

6 

7 

6       (D 

(35 

W 

6 

(5) 

W 

6 

8 

5 

6 

9 

® 

10 

© 

Fig.  103. 


For  the  trailing  point  it  is  shown  in  Fig.  103. 

Fig.  104  illustrates  an  interlocking  plant  in  which 
are  combined  all  three  of  the  primary  elements  already 
referred  to. 


IN  THEOEY  AND  PRACTICE. 


231 


Here  when  either  route  on  the  line  A-B  is  "set  up" 
(the  difference  in  the  routes  being  only  in  the  use  of 
the  signals)  both  derails  on  the  line  C-D,  both  derails 
on  the  line  E-F  and  the  derail  on  the  line  G-H  must 
be  locked  normal.  The  position  of  the  crossovers 
11  and  18  is,  of  course,  immaterial  so  long  as  derails 
8,  10,  20,  22  and  24  are  normal,  so  that  it  is  unneces- 
sary to  have  any  locking  between  them  and  the  derails 
on  line  A-B. 

The  locking  sheet  for  this  arrangement  is  shown  on 
pages  232  and  233. 

There  are  one  or  two  peculiar  points  about  this 
locking  on  which  I  shall  comment. 


In  the  first  place  it  will  be  noted  that  signal  5  gives 
a  route  through  crossover  11,  reversed,  and  back 
through  crossover  18,  reversed,  to  either  F  or  H. 

This  requires  quite  a  bit  of  special  locking  and  in 
actual  practice  is  rarely  done,  as  the  distance  between 
crossovers  11  and  18  is  so  short  that  it  is  assumed  that 
this  loop  around  movement  would  never  be  made 
unless  the  track  on  the  line  E-F  between  the  cross- 
overs was  torn  up  or  otherwise  obstructed,  in  which 
case  trains  could  be  looped  around  by  verbal  orders 
or  hand  signals  given  by  the  leverman. 


232 


RAILWAY  SIGNALING 


LEVER 

LOCKS 

1 

(5) 

2 

C4) 

3 

0)      II 

§30 

4 

95    /i 

l& 

5 

(7)       ® 

©      © 

©       IV 

18 

?7       IV 

18 

©    w     d0)    £0 

S3       M/ 

m    ro 

20      W 

a®    © 

29       W       ©      © 

6 

®     00     (39) 

©       IV 

/8 

?6       IV 

/8 

C®      W 

(!©      ?0 

®       IV 

of    ^o 

Cl)     w     OS)     (8) 

?9       IV       (j£j)      (^ 

7 

®       // 

Of) 

8 

/£ 

18       W 

// 

9 

10       W) 

//      QD 

10 

II        12 

II 

Fig.  105. 


IN  THEORY  AND  PRACTICE. 


233 


LEVER 

£06705 

K 

?0 

££ 

£4 

/3 

© 

14 

@ 

15 

© 

/6 

16 

03) 

11 

si 

18 

19 

/8 

© 

IQ      © 

20 

24- 

!/ 

© 

?2 

/8 

?3 

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?4 

// 

| 

18 

25 

@ 

26 

(D 

© 

(19)     (23) 

11 

C7) 

(9) 

d/)    (®    © 

Id 

|5)       (f9) 

@    iv    d§) 

(4 

W 

c/© 

(7) 

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/8 

GO 

W 

(J/)     Q3) 

£9 

w     ©     Q®     @     ®) 

30 

//      \D     @     $0 

<3/ 

© 

32 

® 

Fig.  106. 


23 i  RAILWAY  SIGNALING 

Derail  lever  10  is  locked  by  its  lock  lever  9,  both 
normal,  and  reversed.  This  is  because  the  same  lever 
throws  the  lock  for  crossover  11.  Now  if  lever  9 
locked  lever  10  reversed  only,  10,  as  already  shown, 
would  have  to  be  reversed  before  9  could  be  moved, 
but  in  case  of  a  route  through  No.  11  reversed,  10 
would  be  locked  normal,  therefore  9  could  not  be 
thrown  to  lock  11. 

For  this  reason  signal  No.  6  must  lock  derail  10, 
reversed,  directly,  and  not  through  the  medium  of 
lock  lever  9,  as  is  the  case  with  the  other  derails. 

Here  too  in  actual  practice  both  ends  of  No.  11 
woud  probably  be  locked  by  one  lever,  as  with  18,  and 
8  and  10  would  either  be  operated  by  switch  and  lock 
movements  or  an  additional  lock  lever  would  be  pro- 
vided for  one  of  them.  The  arrangement  shown 
in  the  figure  is  intended  for  illustrative  purposes. 

A  detector  bar,  fifty  or  fifty-three  feet  long,  is 
a  heavier  load  on  a  lever  than  a  switch,  and  where 
two  bars  are  put  on  one  lever  with  800  to  900  feet  of 
pipe,  it  requires  about  all  the  strength  of  an  ordinary 
man  to  throw  them.  There  is  quite  a  general  ten- 
dency today  to  use  a  separate  lever  for  each  bar 
wherever  possible. 

As  a  general  rule  a  beginner  in  designing  locking 
sheets  should  imagine  himself  in  the  place  of  the 
leverman,  and  see  what  levers  must  be  reversed  to  set 
up  each  route  and  then  see  what  levers  must  be  nor- 
mal to  guarantee  a  safe  passage  to  a  train  over  each 
given  route.  From  this  a  preliminary  locking  sheet 
can  be  made. 

Mr.  A.  M.  Wellington,  in  his  Economic  Theory  of 
Railroad  Location,  says  that  a  locating  engineer  after 
having  picked  out  what  he  thinks  is  the  best  line, 
will  generally,  if  he  looks  at  it  a  second  time,  find 
where  he  can  improve  on  his  first  selection.  This  is 
certainly  true  of  designers  of  locking  sheets.  It  is 


IN  THEORY  AND  PRACTICE.  235 

generally  the  custom  to  have  two  men  draw  up  lock- 
ing sheets  from  the  same  track  plan,  independently 
of  each  other,  and  then  compare  notes.  What  one 
misses  the  other  one  is  likely  to  include.  Where  only 
one  man  can  work  on  it  he  should  draw  up  one 
sheet,  commencing  with  lever  No.  1,  then,  without 
referring  to  the  first  sheet,  draw  up  another,  com- 
mencing with  the  highest  numbered  lever  and  work- 
ing backwards.  After  that  is  finished  compare  the 
two,  lever  by  lever,  and  most  errors  in  each  will  be 
caught.  It  is  no  easy  thing  to  learn,  and  requires  a 
vast  amount  of  practice  to  become  a  proficient  at  it. 

In  the  foregoing  figures  no  special  attention  has 
been  given  to  systematic  numbering  of  the  levers,  and 
no  allowance  has  been  made  for  spare  spaces  which  are 
generally  left  in  each  machine  to  provide  for  any  ad- 
ditions which  may  be  made  thereto  later  on. 

The  numbering  of  the  levers  in  a  mechanical  ma- 
chine depends  somewhat  on  the  type  of  leadout  used. 
Levers  for  wire  connected  signals  are  generally  placed 
together  at  the  ends  of  the  machine,  so  that  the  box 
chain  wheels  which  carry  the  wires  away  from  the 
tower  may  be  placed  at  either  end  of  the  leadout 
platform,  and  the  wires  thus  turned  and  led  away  with- 
out crossing  the  pipe  lines.  In  running  the  pipe  lines 
alongside  of  a  track  it  is  good  practice  to  have  the 
pipe  which  operates  the  function  nearest  the  tower  on 
the  inside  of  the  pipe  run — that  is  nearest  the  track. 
In  this  way  when  it  turns  and  goes  off  to  its  function 
it  will  not  have  to  cross  under  any  other  pipes.  Such 
an  arrangement  as  this  prevents  the  chance  that  in 
case  of  a  cross  pipe's  being  caught  by  something 
dragging  from  a  car  and  being  torn  up,  it  will  also 
tear  up  the  other  pipes  under  which  it  crosses. 

This  is  called  "dropping  off"  on  the  inside  of  the 
pipe  run. 

With  a  rocker  shaft  leadout  almost  any  system  of 


236  RAILWAY  SIGNALING 

numbering  the  pipe  connected  levers  may  be  followed, 
and  the  pipes  so  arranged  as  to  drop  off  inside. 

With  a  crank  or  deflecting  bar  leadout,  however, 
this  is  not  so  easily  done,  and  it  will  be  found  most 
often  convenient  to  draw  up  a  leadout  plan  in  pencil 
and  number  the  levers  according  to  the  way  their  pipes 
drop  off. 

This  method  will  generally  scatter  switch  lock  and 
signal  levers  indiscriminately  through  the  machine, 
but  it  also  as  a  rule  groups  the  levers  in  each  com- 
bination together  so  that  the  leverman  does  not  have  to 
move  so  far  in  setting  up  any  particular  route. 

Some  signal  engineers  prefer  to  group  all  the  dis- 
tant signal  levers  together  at  the  ends  of  the  ma- 
chine, then  the  home  signal  levers,  and  have  all  lock 
and  switch  levers  in  the  center.  With  a  crank  or 
deflecting  bar  leadout  such  an  arrangement  often  re- 
quires a  good  many  extra  cranks  on  the  ground,  and 
although  it  does  well  enough  with  small  machines,  with 
large  ones  it  makes  the  operation  much  less  con- 
venient. 

With  power  machines  the  levers  in  each  combination 
are  generally  grouped  together  and  numbered  accord- 
ingly. 

There  is  no  absolute  rule  for  the  allowance  of  spare 
spaces  to  be  made.  To  leave  twenty-five  per  cent 
of  the  spaces  spare  is  not  a  bad  rule  for  power  ma- 
chines, and  with  mechanical  ones  it  is  largely  a  matter 
of  judgment.  If  a  plant  is  being  put  in  at  a  plain 
single  track  crossing  where  there  is  a  likelihood  of 
double  tracking,  it  is  not  a  bad  idea  to  draw  up  a  pre- 
liminary double  track  plan  with  facing  and  trailing 
point  crossovers  and  passing  track  switches,  and  get 
a  machine  large  enough  for  such  a  combination,  with 
all  unnecessary  levers  left  out — spare  spaces. 

It  is  a  good  rule  to  look  the  ground  over  care- 
fully before  making  up  a  leadout  plan,  as  it  is  some- 


IN  THEORY  AND  PRACTICE.  237 

times  necessary  to  cross  tracks  in  a  way  which  would 
not  be  apparent  from  the  track  plan,  and  this  may 
have  an  effect  on  the  numbering,  and  perhaps  sim- 
plify it. 

The  preparation  of  dog  charts  is  much  more  a  mat- 
ter of  practice  and  skill,  even,  than  is  that  of  locking 
sheets. 

The  object  to  be  attained  is  to  arrange  the  dogs  in 
such  a  way  that  as  few  of  them  will  be  required  as 
possible,  thus  saving  material  and  labor  in  the  con- 
struction of  the  machine.  It  is  quite  possible  to  have 
perfectly  safe  locking  and  to  accomplish  everything 
called  for  in  the  locking  sheet  by  many  different  ar- 
rangement of  dogs.  Most  generally  one  will  be  found, 
however,  more  simple  than  the  rest,  which  to  the  ex- 
pert designer  would  be  the  correct  method  to  em- 
ploy. 

A  very  thorough  knowledge  of  shop  practice  in 
manufacturing  locking  is  a  necessary  part  of  a  good 
designer's  education. 

With  Saxby  and  Farmer  machies  it  is  the  general 
rule  first  to  study  the  locking  sheet  to  find  out  what 
levers  lock  the  same  lever  in  a  certain  position,  and 
also  what  special  locking  is  to  be  provided  for.  The 
latter  is  generally  laid  out  first  so  as  not  to  have  a 
"when"  dog  on  a  locking  bar  adjacent  to  the  locking 
bar  carrying  a  dog  which  drives  through  the  when. 
After  that  the  simple  locking  is  worked  out  from  No. 
1  locking  bar  outward.  An  effort  should  be  made  to 
get  all  the  locking  on  as  few  bars  as  possible.  This 
may  often  permit  of  the  use  of  a  narrower  locking 
bed  than  the  number  of  levers  in  the  machine  would 
require  if  each  lever  had  a  locking  bar  to  itself,  thus 
saving  space  in  the  tower  and  possibly  permitting  the 
use  of  a  larger  machine. 

This  is  something  the  manufacturers  will  not  do 
unless  their  attention  is  called  to  it  when  the  machine 


238  EAILWAT  SIGNALING 

is  ordered,  as  the  rule  is  to  ship  out  machines  with 
their  full  complement  of  locking  bars  whether  all  the 
bars  carry  dogs  or  not. 

In  vertical  locking  the  tappets  take  the  place  of  the 
cross  locks  of  the  Saxby  and  Farmer  type,  and  the 
operation  may  be  said  to  be  reversed  in  that  the  levers 
drive  the  crosslocks  (tappets)  which  in  turn  drive 
the  bars  and  dogs,  while  in  the  Saxby  and  Farmer 
the  levers  drive  the  locking  bars  and  dogs,  which  in 
turn  drive  the  crosslocks. 

To  a  person  who  thoroughly  grasps  this  distinction, 
there  is  no  vital  difference  in  the  method  of  designing 
vertical  locking  from  that  employed  in  designing  that 
for  Saxby  and  Farmer  machines. 

The  special  swing  dogs  with  the  vertical  type  are 
attached  to  the  tappets  and  not  to  the  locking  bars. 
In  each  locking  space  with  a  vertical  locking  bed 
eight  locking  bars,  five  front  and  three  back,  may 
travel.  This  makes  it  easy  to  assemble  a  great  deal 
of  locking  in  a  very  small  vertical  space.  This  un- 
fortunately is  of  no  great  advantage  as  the  width  of 
the  tower  has  to  remain  the  same  anyway. 

When  an  interlocking  machine  is  shipped  out  from 
the  factory,  it  is  taken  apart  and  boxed.  As  it  has 
been  put  together  and  tested,  such  of  the  pieces  as  re- 
quire it  are  marked  with  figures  and  letters  stamped 
on  them  to  show  how  they  are  to  be  put  together. 

With  a  Saxby  and  Farmer  machine  the  crosslocks 
are  all  stamped  with  a  number  and  the  letter  B,  as 
"3  B."  This  means  that  that  crosslock  belongs  in 
bracket  No.  3.  On  each  end  another  number  is 
stamped,  as  2,  6.  This  means  that  the  end  stamped  2 
is  next  to  locking  bar  No.  2,  and  the  end  stamped  6 
is  next  to  the  locking  bar  of  that  number.  This 
shows  at  once  the  exact  position  in  the  locking  bed 
of  this  particular  piece  of  crosslock.  The  locking 
bars  are  numbered  as  already  described.  The  dogs 


IN  THEOEY  AND  PRACTICE.  239 

are  left  rivetted  to  them  so  there  is  no  necessity  to 
number  them.  The  drivers  are  also  left  rivetted  to 
the  bars,  but  as  a  locking  bar  may  be  cut  and  driven 
by  two  or  more  levers,  each  driver  has  the  number 
of  its  lever  stamped  on  it. 

With  vertical  locking-  the  locking  bars  are  shipped 
out  with  the  dogs  rivetted  to  them.  The  bars  are 
lettered  T.  M.  and  B.,  standing  for  top,  middle  and 
bottom.  With  the  front  locking  there  are  two  tops 
and  two  bottoms.  The  drilling  by  which  the  screws 
holding  the  dogs  to  the  bars  is  made  in  the  dogs, 
shows  which  is  the  upper  and  which  the  lower  top  or 
bottom.  The  shape  of  the  dogs  shows  which  is  the 
front  and  which  the  back  locking. 

Other  parts  of  the  machine  are  numbered  so  that 
there  is  no  difficulty  in  assembling  it. 

There  is  another  point  which  is  a  factor  in  some 
interlocking  plants,  but  not  in  all,  which  should  be 
called  to  the  student's  attention.  This  is  the  locking 
of  drawbridges. 

It  is  the  general  custom  now-a-days  to  have  one 
lever  in  the  interlocking  machine  lock  the  engine  by 
which  the  movable  part  of  the  bridge  is  put  in  mo- 
tion, so  that  it,  the  engine,  cannot  be  started  when  this 
lever  is  reverse^.  This  can  be  done  by  using  an  or- 
dinary bolt  lock  or  facing  point  lock  connected  to  the 
lever  of  the  engine,  and  also  to  that  of  the  machine. 
By  having  all  other  levers  in  the  machine  either 
directly  or  indirectly  lock  this  first  lever  reversed, 
no  lever  in  the  machine  can  be  reversed  until  the  en- 
gine is  cut  out,  and  the  engine  cannot  be  cut  in  until 
everything  is  normal  again.  Another  lever  in  all 
drawbridge  machines  is  devoted  to  hooking  and  un- 
hooking the  bridge  couplers.  The  whole  combination 
had  best  lock  this  lever  reversed,  also,  so  as  to  insure 
that  the  pipe  lines  or  wires,  if  a  power  plant,  are 


LEVER 

LOCKS 

1 

®                ®                 9 

2 

® 

3 

® 

4 

6 

6 

7 

® 

8 

® 

9 

®                @ 

NS4    OPERATES 

BRIDGE  LOCK 

A/95             •» 

•••      COUPLER 

MS  6      L0CX3 

ENGINE 

9       8 


/BUTT 


Fig.  107. 


IN  THEORY  AND  PRACTICE.  241 

coupled  together  at  the  coupler  before  any  of  them 
are  moved,  or  current  applied. 

The  lifting  or  spreading  rails  at  the  end  of  the 
bridge  are  treated  as  switches,  but  are  locked  with 
facing  point  locks  of  a  much  heavier  construction  than 
those  used  for  switches. 

Fig.  107  shows  a  track  plan  locking  and  dog  sheet 
for  a  single  track  drawbridge  taken  from  actual  prac- 
tice, which  will  serve  to  illustrate  what  has  preceded 
on  this  head. 

Sometimes  where  very  unimportant  lines  cross  lines 
of  heavier  traffic,  and  it  is  considered  necessary  to 
protect  the  crossing  with  interlocking,  the  expense  of 
permanent  levermen  is  avoided  by  putting  the  inter- 
locking machine  in  a  building  which  can  easily  be  en- 
tered by  trainmen  of  the  inferior  line.  Trains  on  this 
line  are  stopped  at  the  home  signal  and  one  of  the 
trainmen  goes  ahead  and  acts  temporarily  as  leverman, 
until  the  train  has  pulled  over  the  crossing  far  enough 
for  its  rear  end  to  clear  the  farther  derail,  when  it 
stops  and  the  trainman  restores  the  routes  to  their 
normal  position,  after  which  he  boards  the  train  and 
it  proceeds. 

In  such  cases,  I  will  say  in  passing,  that  the  signals 
and  derails  on  the  superior  line  stand  normally  re- 
versed, so  that  trains  on  that  route  always  find  the 
signal  clear  unless  the  crossing  is  actually  in  use  by  a 
train  on  the  other  line. 

To  prevent  the  possibility  that  an  inexperienced  or 
careless  trainman  might  leave  the  route  set  up  for 
the  inferior  line,  which  would  mean  leaving  the  sig- 
nals at  caution,  and  stop,  and  the  derails  open  on  the 
superior  line,  and  would  cause  trains  on  that  line  to 
stop  unnecessarily,  one  of  the  levers  in  the  inter- 
locking machine  which  is  locked  reversed,  either 
directly  or  indirectly  by  the  entire  combination  in  ad- 
dition to  some  other  function  which  it  may  perform, 


242 


RAILWAY  SIGNALING 


also  locks  the  door  of  the  cabin  (such  machines  are 
usually  arranged  for  horizontal  leadout,  and  are 
placed  in  a  one-story  building  which  is  called  a  cabin 
in  contradistinction  to  the  name  tower  applied  to  a 
two-story  building),  until  all  routes  are  returned  to 


LEVER 

LOCKS 

1 

® 

Z 

3 

3 

4 

0 

(§)         3         ©        © 

3 

3 

6 

(5) 

LEVERS  7,2.4,5 

,  6  ARE  KEPT  IN  THE  REVERSE 

POSITION  AND  ARE 

ONLY  SET  NORMAL    WHILE 

ELECTRIC  CAR  IS  USING   THE  CROSSING  . 

Fig.  108. 

their  normal  condition,  thus  holding  the  temporary 
leverman  a  prisoner  in  the  cabin  until  he  has  placed  all 
signals  and  derails  as  they  should  be.  Something 
similar  to  a  facing  point  lock  is  generally  used  for 
the  door  lock. 
At  crossings  of  steam  railroads  and  electric  inter- 


IN  THEORY  AND  PEACTICE.  243 

urban  lines  this  condition  comes  up  frequently,  and 
the  same  results  may  be  obtained  by  using  double 
derails,  as  with  a  door  lock. 

Fig.  108  illustrates  such  an  arrangement,  giving 
also  the  locking  sheet.  In  this  particular  case  no  de- 
rails are  placed  in  the  track  of  the  steam  railroad. 
The  plan  is  taken  from  actual  practice  and  no  derails 
were  deemed  necessary  under  the  conditions  which 
existed. 

The  only  reason  that  such  a  plan  will  not  answer 
with  an  inferior  steam  road,  is  that  the  outside  de- 
rails would  have  to  be  placed  a  full  train  length  from 
the  inside  ones,  which  would  make  them  too  far  away 
to  be  operated  with  safety  by  a  pipe  line.  The  door 
lock  does  just  as  well  and  is  cheaper  than  a  long  pipe 
line  would  be. 

Besides  the  locking  sheet  and  dog  sheet,  what  is 
known  as  a  manipulation  chart  should  be  drawn  up 
for  each  interlocking  plant. 

This  manipulation  chart  is  a  track  plan,  not  usually 
drawn  to  scale  and  generally  very  much  larger  than 
the  regular  track  plan.  On  this  all  the  lever  num- 
bers are  shown  at  their  respective  functions  in  large 
block  figures,  so  that  they  may  be  read  from  some 
little  distance.  Block  letters  are  used  to  distinguish 
the  different  routes.  Beneath  or  alongside  of  the 
track  plan  each  route  is  shown,  as  A  to  B,  C  to  D, 
E  to  F,  etc.,  etc.,  and  after  the  route  the  numbers  of 
the  levers  which  must  be  reversed  in  order  to  "set 
up"  that  route.  These  numbers  are  given  in  the 
sequence  in  which  the  levers  are  to  be  reversed. 

These  manipulation  charts  are  always  drawn  with 
the  top  of  the  plan  representing  the  side  of  the  track 
farthest  away  from  the  leverman  as  he  stands  facing 
the  machine,  so  that  he  has  the  track  plan  before  him, 
just  as  it  would  look  if  he  looked  down  at  the  ground 
from  a  window  behind  the  machine. 


244 


RAILWAY  SIGNALING 


Either  a  blue  or  white  print  copy  of  the  manipula- 
tion chart  should  be  framed  neatly  and  hung  up  in 
the  tower  behind  the  machine,  so  that  the  leverman  will 

ARCTIC  fie  ANTARCTIC  RY  CO. 

EQUATOR  ,  BRAZIL. 


MANIPULATION 


FROM  To 


A 
c 


;E  LEVERS. 


8 


8 


3 


6 


10 

9 


12 
13 


Fig.  109. 


always  have  it  in  front  of  him  to  refer  to  as  an  aid 
in  handling  the  levers.  As  one  print  of  this  plan  very 
likely  may,  and  frequently  does  last  a  number  of 


IN  THEORY  AND  PRACTICE.  245 

years,  it  pays  to  spend  a  little  time  on  it,  and  color 
the  signals  and  tracks  so  as  to  make  them  more 
conspicuous  and  give  the  whole  drawing  a  finished 
look,  which  adds  very  much  to  the  general  appearance 
of  the  operating  room  of  the  tower. 

Black  block  letters  and  figures  of  various  sizes  are 
to  be  had  which  are  gummed  on  the  back  like  a  postage 
stamp,  and  a  great  deal  of  draftsman's  time  may  be 
saved,  and  a  very  neatly  lettered  print  secured,  by 
using  such  figures  and  letters  on  the  tracing.  By 
using  a  straight  edge  and  being  careful  just  as  good 
results  may  be  had  as  with  the  laborious  hand  let- 
tering which  some  draftsmen  put  in  on  these  tracings. 

Levermen  generally  become  so  familiar  with  their 
machines  in  a  few  days  that  they  rarely  have  to  refer 
to  the  manipulation  chart  even  at  large  plants,  but  new 
men  cannot  be  expected  to  handle  a  machine  promptly 
unless  one  is  before  them,  and  as  men  may  change  at 
any  time  a  correct  manipulation  chart  should  be  in 
all  towers  at  all  times. 

Fig.  109  gives  a  typical  manipulation  chart  for  the 
interlocking  shown. 

As  an  additional  aid  to  the  levermen  the  levers,  or 
at  least  that  part  of  them  which  appears  above  the 
floor,  except  the  handles,  which  are  polished,  are 
painted  various  colors  to  correspond  with  the  function 
which  they  perform. 

For  instance,  where  distant  signal  blades  are 
painted  green,  and  home  signal  blades  red,  the  dis- 
tant signal  levers  are  painted  green,  home  signal  levers 
red,  switch  levers  black,  lock  levers  blue,  switch  and 
lock  levers  half  black  and  half  blue. 

Before  putting  a  plant  in  service,  the  locking  of  the 
machine  should  be  thoroughly  checked.  The  best 
way  to  do  this  is  first  to  go  carefully  over  it  with 
the  dog  sheet,  bar  by  bar,  dog  by  dog,  and  tappet 
by  tappet.  Then  by  reversing  all  the  levers  in  the 


246  RAILWAY  SIGNALING 

machine  for  each  given  route  and  testing  all  the 
other  levers  it  can  soon  be  seen  if  anything  is  left  un- 
locked which  should  be  locked. 

If  any  changes  ever  have  to  be  made  in  the  locking 
of  a  machine  once  in  service,  they  should  be  first 
drawn  in  colors  on  a  copy  of  the  dog  sheet  and 
thoroughly  checked,  after  which  the  plan  should  be 
given  to  a  reliable  mechanic  to  make  the  change.  A 
dog  misplaced  in  a  machine  may  leave  a  dangerous 
flaw  in  the  locking  combination  which  may  escape 
detection  for  years,  and  too  much  pains  cannot  be 
taken  to  insure  that  changes  are  properly  made. 


CHAPTER  XVII. 

POWER  DISTANT  SIGNALS CROSSING  BARS- — TIME  LOCKS 

— ELECTRIC    LOCKING — SWITCH    PROTEC- 
TION   SIGNALS. 

In  an  earlier  chapter  attention  was  called  to  the  fact 
that  distant  signals  at  mechanical  interlocking  plants 
were  not  always  operated  by  pipe  or  wire  lines. 

In  fact,  it  has  become  very  general  practice  to  use 
what  are  known  as  power  distant  signals. 

As  a  general  thing  such  signals  are  operated  by 
electric  motors,  current  to  run  which  is  supplied  by  a 
local  battery  of  Lalande  cells.  The  motors  used  for 
such  signals  are  constructetd  to  operate  on  ten  volts 
pressure. 

At  one  time  signals,  the  motive  power  for  which 
was  carbonic  acid  gas  under  very  great  pressure,  were 
used  to  some  extent  for  this  purpose,  but  motor  signals 
have  been  so  much  improved  of  late  years  that  at 
present  they  virtually  monopolize  the  field. 

With  the  gas  signals,  gas  was  admitted  to  a  cylin- 
der which  operated  the  signal  blade  by  a  valve  con- 
trolled by  an  electro  magnet  much  as  is  done  with 
electro  pneumatic  interlocking  signals. 

Where  power  distant  signals  of  any  type  are  used, 
they  are  either  operated  by  a  separate  lever  in  the 
machine,  just  as  if  they  were  mechanical  signals,  or 
less  frequently  by  the  same  lever  which  operates  the 
home  signal. 

The  former  practice  is  preferable,  because  it  allows 
247 


248  RAILWAY  SIGNALING 

independent  use  of  the  distant  signal,  although  with 
the  other  an  arrangement  may  easily  be  made  by  which 
a  train  on  passing  the  distant  signal  will  automatically 
set  it  at  caution  before  the  home  signal  is  set  at  stop 
by  the  leverman. 

Where  separate  levers  are  used,  the  locking  in  the 
machine  is  the  same  as  with  mechanical  signals,  i.  e., 
the  distant  signal  lever  locks  the  home  signal  lever 
reversed. 

The  general  arrangement  is  to  equip  the  distant 
signal  lever  in  the  tower  with  a  mechanical  circuit 
controller.  Three  wires  are  run  from  the  tower  to  the 
distant  signal,  two  of  these  are  attached  to  the  coils 
of  a  relay  at  the  signal,  the  other  is  attached  to  a  me- 
chanical circuit  controller  connected  to  the  arm  plate 
of  the  distant  signal.  A  short  connection  is  made  be- 
tween the  other  side  of  this  circuit  controller  and  one 
of  the  other  wires  through  the  local  battery  as  will  be 
more  fully  explained  presently.  This  latter  wire,  there- 
fore, acts  as  a  common,  and  is  so  designated. 

At  the  tower  the  common  is  connected  to  the  nega- 
tive side  of  a  local  battery  there  and  the  other  wire 
leading  to  the  relay,  known  as  the  control  wire,  is 
broken  through  the  circuit  controller  attached  to  the 
lever,  and  then  connected  to  the  positive  pole  of  the 
battery.  When  the  distant  signal  lever  is  reversed, 
circuit  is  closed  through  its  circuit  controller,  and  cur- 
rent flows  through  the  magnet  coils  of  the  relay,  caus- 
ing it  to  "pick  up." 

The  circuit  of  the  local  battery  at  the  signal  is  car- 
ried through  the  motor,  and  from  there  to  the  front 
contact  of  the  relay.  When  the  relay  is  picked  up, 
therefore,  circuit  is  closed  through  the  motor,  it 
revolves  and  brings  the  signal  blade  to  clear.  When 
the  leverman  returns  the  lever  to  normal,  circuit 
through  the  relay  is  broken  by  the  circuit  controller 
attached  to  the  lever.  The  relay  drops  and  breaks  the 


IN  THEORY  AND  PRACTICE.  249 

local  circuit,  which  releases  the  signal  blade  and  allows 
it  to  return  to  normal  by  gravity. 

The  third  wire  leading  from  the  tower  to  the  signal 
is  called  the  lock  wire.  Its  tower  end  is  attached  to 
an  electro  magnet  fastened  to  the  frame  of  the  inter- 
locking machine.  The  armature  of  this  magnet  is 
fastened  to  a  latch  or  hook  arranged  to  engage  a  notch 
in  a  piece  of  steel  attached  to  the  home  signal  lever  in 
such  a  way  that  the  home  signal  lever  cannot  be 
moved,  or  in  some  cases  its  latch  cannot  be  put  down, 
when  this  magnet  is  de-energised.  This  arrangement 
is  known  as  an  electric  lock.  They  are  made  in  a  num- 
ber of  varieties,  by  different  makers,  and  to  fit  differ- 
ent machines. 

At  the  signal  end,  the  lock  wire,  as  before  stated,  is 
broken  through  a  circuit  controller  attached  to  the 
arm  plate  of  the  signal.  From  this  circuit  controller 
connection  is  made  to  the  local  signal  battery,  and 
from  there  to  common.  While  the  distant  signal  blade 
is  at  clear  the  lock  circuit  is  broken,  so  that  in  case 
the  signal  blade  should  fail  to  return  to  normal  when 
the  leverman  so  placed  the  distant  signal  lever,  the 
home  signal  lever  would  either  be  locked  reversed  or  its 
latch  would  be  locked  up  so  that  although  the  lever 
might  be  returned  to  normal  it  could  not  be  latched 
there,  and  the  preliminary  locking  would  hold  all  con- 
flicting levers  in  the  machine  locked,  so  that  the  route 
could  not  be  changed  and  the  leverman  would  be 
warned  that  the  distant  signal  had  not  returned  to 
normal.  This  arrangement  is  known  as  back  locking. 

Where  the  home  signal  lever  also  operates  the  dis- 
tant signal,  the  circuit  controller  in  the  tower  is 
attached  to  it.  The  back  locking  arrangement  is  virtu- 
ally the  same.  The  electric  locks  are  so  arranged  that 
when  the  latch  is  down  they  break  the  circuit  in  that 
way,  preventing  an  unnecessary  drain  on  the  signal 
battery. 


250 


EAILWAY  SIGNALING 


Fig.  1 10  shows  typical  circuits  for  both  arrange- 
ments. 

There  has  been  some  discussion  amongst  signal 
engineers  lately  as  to  whether  this  back  locking  might 
not  be  dispensed  with  on  the  ground  that  these  signals 
rarely  if  ever  fail  to  return  to  normal,  but  up  to  the 
present  it  cannot  be  said  to  be  good  practice  to  give 
it  up. 

So  far  we  have  considered  interlocking  only  in  its 
most  simple  form.  We  have  taken  it  for  granted  that 
the  leverman,  having  once  set  up  a  route  for  an 
approaching  train,  would  not  take  it  away  again  and 


'OCt//s  fo!>s0n  £o#ery 


f/fc  fr/t  LocJt  on  Abtnt  Sfgnot  Itrtr  6 
t'afch  up  rv/tt>  £t*er  in  rtfr-mo/  fbsit'on 


t        .  .          .     ivfi. 

Fig.  110. 

open  the  derails  in  the  very  face  of  that  train  as  it 
approached,  and  after  it  had  come  so  close  to  the 
derail  that  there  would  be  no  possibility  of  its  being 
stopped  before  it  had  run  off  the  track,  or  that  with 
a  short  train  or  single  car  or  engine  standing  on  a 
crossing  between  the  derails,  he  would  not  set  up  the 
opposing  route  for  an  approaching  train,  and  thus 
invite  a  collision  right  on  the  crossing  itself. 


IN  THEORY  AND  PRACTICE. 


251 


Unfortunately,  levermen,  like  the  rest  of  us,  are  not 
infallible  and  do  sometimes  make  mistakes. 

The  second  of  the  possibilities  mentioned  above, 
viz:  a  collision  on  the  crossing,  is  often  guarded 
against  by  using  what  are  known  as  crossing  bars. 
These  are  neither  more  nor  less  than  detector  bars 
placed  close  to  the  crossing  frogs  so  that  any  car  or 
engine  standing  on  the  crossing  must  have  at  least 
one  wheel  on  the  bar  or  bars.  These  bars  are  operated 


Fig.  111. 

by  a  lever  in  the  machine.  This  lever  usually  locks 
the  derails,  in  the  line  on  which  the  bars  it  operates 
are  placed,  reversed,  and  is  in  turn  locked  reversed  by 
the  home  signals.  In  this  way  the  crossing  bars  must 
be  reversed  before  a  route  can  be  set  up  and  must  be 
returned  to  normal  before  that  route  can  be  changed. 

If,  therefore,  a  wheel  is  standing  on  the  bar,  the 
route  cannot  be  changed  and  the  derails  in  the  oppos- 
ing route  must  remain  normal. 

The   foregoing  applies  more  particularly  to  cases 


252  RAILWAY  SIGNALING 

where  there  are  separate  crossing  bars  for  each  route. 
With  crossings  of  an  angle  approaching  ninety  de- 
grees, the  bars  have  to  be  made  fifty  feet  long,  one 
on  each  side  of  the  crossing  on  each  route,  as  shown 
in  Fig.  in.  This  is  necessary  because  a  truck  might 
stand  on  the  crossing  itself  and  unless  there  was  a  bar 
on  either  side  the  other  truck  might  not  stand  on  one. 
With  crossings  of  a  sharp  angle,  25-foot  bars  may  be 
used  and  four  of  them  put  on  one  lever,  as  shown  in 
Fig.  in,  also.  Here  it  is  easily  seen  that  a  truck 
standing  on  the  crossing  will  hold  down  the  bar. 

In  such  cases  it  is  generally  the  custom  to  have  the 
crossing  bar  lever  lock  all  the  derail  levers  normal  and 
reversed,  and  then  to  have  each  of  the  home  signal 
levers  lock  the  crossing  bar  lever  reversed.  In  this 
way  no  signal  can  be  cleared  until  the  crossing  bar 
lever  has  been  reversed,  but  when  reversed  the  cross- 
ing bar  lever  locks  all  derail  levers  in  whichever  posi- 
tion they  may  be  in  at  the  time.  Therefore,  the  cross- 
ing bar  lever  must  be  returned  to  normal  before  a 
route  can  be  changed,  which,  if  anything  is  standing 
on  the  bar,  cannot  be  done.  Another  locking  arrange- 
ment which  accomplishes  the  same  result  is  to  have 
one  derail  lever  lock  the  crossing  bar  lever  normal 
and  the  other  derail  lever  lock  it  reversed.  As  the 
derail  levers  lock  each  other  normal,  a  route  cannot 
then  be  changed  without  moving  the  crossing  bars, 
which  is  the  object  sought.  Although  with  this  arrange- 
ment one  derail  lever  may  be  set  normal  without  first 
moving  the  bar,  the  other  derail  lever  cannot  be 
reversed  until  the  bar  has  been  thrown. 

Crossing  bars  do  not,  however,  in  any  way,  prevent 
a  leverman  from  changing  routes  as  fast  as  he  is  able 
to  throw  the  levers  if  nothing  is  standing  on  the  cross- 
ing bars,  and  some  very  serious  derailments  have  been 
caused  by  levermen  after  giving  a  train  a  route,  sud- 
denly becoming  rattled  and  throwing  the  levers  back  to 


IN  THEORY  AND  PRACTICE. 


253 


Fig.  112. 


254  -RAILWAY  SIGNALING 

their  normal  positions,  thus  opening  the  derail  in  the 
very  face  of  the  train. 

To  prevent  this  the  so-called  time  lock  has  been 
devised.  One  of  these  devices  applied  to  a  Saxby  and 
Farmer  machine  is  shown  in  Fig.  112. 

It  consists  of  a  quite  heavy  rack  placed  vertically 
in  an  iron  case,  in  which  it  may  move  up  and  down. 
This  rack  acts  on  a  double  pendulum  much  as  the 
weight  of  a  clock  acts  on  its  pendulum.  Every  time 
the  pendulum  swings  it  releases  the  rack  one  tooth. 
The  rack  may  be  arranged  so  that  after  being  shoved 
up  as  far  as  it  will  go  it  will  take  from  a  minute  to  a 
minute  and  a  half  to  "run  down,"  after  being  released. 
This  rack  has  a  notch  in  its  front  side  near  the  top 
which  notch  engages  a  roller  pinned  in  the  end  of  a 
piece  of  cross  lock  laid  in  a  bracket  in  the  locking  bed. 
When  the  notch  in  the  rack  is  opposite  this  roller  in 
the  cross  lock,  it,  the  cross  lock,  is  loose,  but  as  soon 
as  the  notch  is  moved  past  the  roller  the  un-notched 
part  of  the  rack  pushes  the  cross  lock  toward  the  front 
of  the  machine  and  holds  it  fast  there. 

The  rack  is  not  connected  directly  to  the  lever,  but 
simply  rests  on  the  end  of  the  shaft  which  is  moved 
up  and  down  as  the  lever  is  alternately  reversed  and 
set  normal.  When  the  lever  is  reversed,  the  rack  is 
pushed  up  and  is  held  up  as  long  as  the  lever  remains 
in  its  reversed  position.  As  the  notch  in  the  rack  is 
so  placed  that  the  crosslock  is  free  only  when  the  rack 
is  down,  the  locking  is  maintained  during  the  time  the 
rack  is  up.  Now  when  the  leverman  returns  the  lever 
to  normal  he  removes  the  support  from  the  lower  end 
of  the  rack.  It  commences  to  fall  by  gravity,  starting 
the  pendulum  which  checks  its  fall  at  every  notch, 
thereby  retarding  its  downward  progress  enough  to 
take  up  a  minute  or  a  minute  and  a  half's  time  before 
the  rack  reaches  the  end  of  its  fall,  and  brings  the 


IN  THEORY  AND  PRACTICE. 


255 


notch  in  its  side  opposite  the  roller  in  the  end  of  the 
crosslock,  thereby  releasing  the  locking. 

Fig.  113  shows  the  method  of  applying  a  time  lock 
to  a  vertical  locking  machine,  and  Fig.  114  a  method 
by  which  one  time  lock  may  be  arranged  so  that  sev- 
eral levers  will  operate  it.  The  crank  arms  aaa  by 
which  the  levers  are  attached  to  the  small  rocking 


Fig.  113. 


shaft  b  are  idle  on  the  rocking  shaft.  The  crank  arms 
c  c  c  c,  however,  are  rigidly  attached  to  it.  When  a 
lever  is  reversed  its  crank  arm  a  engages  the  crank 
arm  c  next  to  it  and  revolves  the  rocking  shaft,  shov- 


256 


RAILWAY  SIGNALING 


ing  up  the  rack  of  the  time  lock.  If  any  other  of  the 
levers  is  reversed  afterwards  its  crank  a  simply  turns 
loosely  on  the  rocking  shaft.  If,  however,  the  first 
lever  is  returned  to  its  normal  position,  the  second  one 
still  holds  the  time  lock  up. 

It  is  usual  to  have  the  time  lock  operated  by  the 


Fig.  114. 

home  signal  levers  and  to  have  the  cross  lock  which 
the  time  lock  drives  lock  all  the  derail  levers  normal, 
and  reversed.  In  this  way  a  home  signal  can  be  set  at 
normal  at  any  time,  but  the  derails  cannot  be  changed 
until  the  time  lock  has  run  down. 

Although  there  is  little  doubt  that  the  use  of  time 
locks,  which  prevents  a  leverman's  making  a  mistake 


IN  THEORY  AND  PRACTICE.  257 

through  over-haste  or  from  excitement,  virutally  elimi- 
nates the  chance  of  any  mistakes  being  made,  there 
are  nevertheless  those  who  are  not  satisfied  with  this, 
and  electricity  has  been  brought  into  play  to  insure  yet 
greater  security  theoretically  than  is  given  by  time 
locking. 

This  is  done  by  what  is  known  as  electric  route  lock- 
ing. An  explanation  of  the  modus  operandi  of  electric 
route  locking  requires  a  prior  explanation  of  the  track 
circuit. 

It  is  by  the  use  of  the  track  circuit  that  all  automatic 
signaling  is  accomplished,  as  well  as  route  locking, 
the  ringing  of  highway  alarm  bells  and  in  many  cases 
the  operation  of  annunciators.  I  shall,  therefore,  go 
into  the  subject  fully  here  and  explain  its  application 
to  other  purposes  as  we  come  to  them. 

In  the  first  place,  any  piece  of  railroad  track  which 
is  to  be  signaled  automatically  or  used  for  electric 
route  locking,  is  divided  into  sections  by  placing 
insulated  joints  in  the  rails  as  shown  at  "a"  in  Fig.  115. 
These  insulated  joints  are  made  by  inserting  a  thick- 
ness or  two  of  vulcanized  fibre  cut  into  the  shape  of 
the  rail  section  and  called  the  "end  post"  between  the 
ends  of  the  rails ;  a  plate  of  fibre  or  wood  is  laid 
between  the  angle  bars  and  the  rails  and  the  bolts  are 
encased  in  fibre  bushings  so  that  no  metal  touches  one 
rail  which  in  turn  touches  other  metal  which  touches 
the  other  rail.  No  electrical  connection,  therefore, 
exists  between  the  two  rails.  The  rails  between  the 
ends  of  the  section  are  bonded  together  with  No.  8 
galvanized  wire  extending  around  the  angle  bar  and 
plugged  into  the  web  of  the  rails  with  pins  of  crescent 
shaped  section  called  channel  pins.  Two  bond  wires 
are  usually  used  at  each  joint  so  that  if  one  breaks  the 
other  one  keeps  the  connection.  This  bonding  is  neces- 
sary to  insure  the  current's  having  a  path  of  low 
resistance,  as  the  scale  on  rails  and  angle  bars  is  not 
always  a  good  electrical  conductor. 


258 


EAILWAY  SIGNALING 


The  sections  are  made  from  2,500  feet  to  5,000  feet 
long,  according  to  conditions,  or  shorter  for  electric 
route  locking.  Good  broken  stone  ballast  will  stand 
longer  sections  than  clayey  gravel  or  cinders.  The 
only  advantage  in  long  sections  is  to  economize  on  the 
use  of  material,  as  will  be  shown  later. 

At  one  end  of  each  section  is  a  battery  consisting  of 


jhsutafed  Joinf 


SECTION 


'•    2500   to  5OOO  ft.  ir>  lerxjjh- 


Channel '  ftr> 


Fig.  115. 

two  or  three  cells  of  gravity  battery.  These  cells  are 
placed  one  above  the  other  in  a  circular  iron  box  called 
a  battery  chute  about  7  feet  long  and  sunk  into  the 
ground,  so  as  to  get  below  frost  in  winter.  A  wooden 
elevator  is  fitted  inside  this  chute  so  that  the  battery 
can  be  drawn  up  and  examined  at  any  time  without 
disturbing  it.  This  battery  is  generally  connected  in 
multiple  in  order  to  reduce  its  internal  resistance. 

One  pole  of  this  battery  is  connected  to  one  rail  of 
the  section  and  the  other  pole  to  the  opposite  rail  as 
atBB,  Fig.  115. 

So  far  the  circuit  through  the  battery  is  open,  as 
there  is  no  connection  between  the  two  rails  at  the 
other  end  of  the  section.  In  order  to  complete  the 
circuit,  therefore,  a  relay  is  attached  to  the  rails 
there — one  side  of  its  coils  to  one  rail  and  the 
other  side  to  the  other  rail.  This  completes  the  circuit 


IN  THEORY  AND  PRACTICE.  259 

and  the  current  flows  from  the  battery  along  one  rail 
as  shown  by  the  arrows  in  Fig.  115  to  the  connection 
to  the  relay,  along  the  wire  which  connects  the  relay 
to  the  rail,  through  the  coils  of  the  relay,  down  the 
wire  connecting  the  relay  to  the  other  rail  along  the 
other  rail,  in  the  opposite  direction,  to  the  wire  which 
connects  it  with  the  other  pole  of  the  battery  and  back 
to  the  battery. 

The  passing  of  this  current  through  the  coils  of  the 
relay  energises  them. 

So  far  we  have  a  simple  track  circuit. 

In  the  condition  described  with  the  relay  picked  up, 
suppose  a  pair  of  wheels  to  enter  the  section  as  shown 


Fig.  116. 

by  the  dotted  lines  at  D,  Fig.  115. 

The  wheels  and  axle,  being  of  large  mass,  offer  an 
infinitesimal  resistance  to  an  electric  current,  while 
the  relay  coils  are  wound  to  offer  quite  an  appreciable 
resistance.  The  bulk  of  the  current,  as  is  always  the 
case,  takes  the  path  of  least  resistance  and  goes  across 
through  the  wheels  and  axle. 

This  de-energises  the  relay  coils,  as  there  is  not 
enough  current  left  going  through  them  to  hold  up  the 
armature,  which  falls  away  by  gravity  into  the  posi- 
tion shown  at  C,  Fig.  115. 

If  the  circuit  from  another  battery  is  connected  in 
such  a  way  that  one  pole  is  attached  to  the  hinge 
of  this  lever  and  the  other  pole  to  the  front  con- 
tact point,  when  the  relay  is  picked  up  this  circuit 


260  RAILWAY  SIGNALING 

is  closed  and  a  current  will  flow  through  it,  when  the 
relay  is  down  this  circuit  will  be  broken.  The  relay, 
therefore,  acts  exactly  like  a  push  button  which,  when 
one  pushes  down  on  it,  closes  the  circuit  and  lets  cur- 
rent flow  through  it.  When  it  is  released  the  spring, 
instead  of  gravity  as  with  the  relay,  throws  the  con- 
tacts apart  and  breaks  the  circuit. 

The  foregoing  is  all  there  is  to  a  track  circuit. 
Where  switches  come  into  a  section,  special  provision 
has  to  be  made  to  insulate  them  in  such  a  way  that 
the  current  from  the  track  battery  will  not  cross  from 
one  rail  to  the  other  through  the  switch  rods. 

Fig.  116  shows  a  typical  way  of  doing  this. 

We  will  now  go  on  to  consider  the  application  of  a 
track  circuit  to  electric  route  locking. 

There  are  numerous  ways  in  which  the  principles 
of  electric  locking  may  be  applied  to  an  interlocking 
plant.  One  of  the  earliest  methods  adopted  and  that 
from  which  more  elaborate  arrangements  have  been 
evolved  is  illustrated  on  page  261.  Here  the  track  cir- 
cuit extends  from  one  derail  to  the  other  in  each  line, 
being  carried  around  the  crossing  itself  by  long  bond 
wires  a  a  b  b.  R  is  the  track  relay  which  is  common 
to  either  line.  E  is  a  local  battery,  usually  placed  in 
the  tower,  circuit  from  which  passes  through  the  front 
contact  of  relay  R,  and  from  there  through  a  front 
contact  of  another  relay  S,  from  thence  it  goes  through 
the  coils  of  the  electric  lock  F,  and  from  there  through 
a  connection  in  a  hand  release  T,  the  use  of  which  will 
be  explained  further  on,  and  back  to  the  point  c, 
whence  it  passes  through  circuit  controllers  attached 
to  the  home  signal  levers,  and  back  to  the  battery. 

It  should  be  remarked  that  just  after  leaving  E  the 
current  is  divided  at  a  point  d.  We  have  just  traced 
out  the  path  of  the  current  which  goes  through  the 
front  contact  of  relay  R.  We  will  now  follow  that 
part  of  the  current  which  leaves  the  former  circuit 


IN  THEORY  AND  PRACTICE. 


261 


262  RAILWAY  SIGNALING 

at  d.  This,  it  will  be  noted,  has  a  path  through  another 
front  contact  of  relay  S,  to  point  e,  through  the  coils 
of  relay  S  to  c,  and  back  to  battery.  This  part  of  the 
current,  therefore,  serves  to  energise  relay  S.  A  pecu- 
liar condition  exists  here,  which  should  be  carefully 
noted.  That  is,  that  the  circuit  by  which  relay  S  is 
energised  is  completed  by  its  own  front  contact.  Now 
when  the  leverman  reverses  home  signal  lever  13,  in 
order  to  give  the  route  A-B,  he  breaks  circuit  through 
lock  F,  which  is  placed  on  derail  lever  4,  and  locks 
that  lever  reversed,  and  also  the  circuit  through  relay 
S,  which  drops  its  armature.  Relay  R,  however,  holds 
up  until  the  first  pair  of  wheels  enters  the  track  sec- 
tion, when  it  drops.  Now  if  the  leverman  restores 
lever  3  to  normal  while  some  part  of  the  train  is  still 
in  the  track  section,  he  closes  circuit  through  relay  S  by 
way  of  the  back  contact  of  relay  R.  This  causes  relay  S 
to  pick  up.  In  this  position  as  soon  as  the  last  pair 
of  wheels  passes  out  of  the  track  section  relay  R  picks 
up ;  this  completes  the  original  circuit  through  lock  F, 
so  that  the  lock  picks  up,  thereby  releasing  derail  lever 
No.  4,  which  may  then  be  returned  to  normal,  and  the 
plant  is  ready  for  a  movement  through  it  in  any 
direction. 

If  the  leverman  should  fail  to  return  his  home  signal 
to  normal  until  after  relay  R  has  picked  up,  he  must 
use  his  hand  release  in  order  to  get  his  derail  lever 
normal  again. 

These  hand  releases  are  made  in  many  ways.  Some- 
times they  are  an  ordinary  electric  switch,  enclosed  in 
a  glass  case,  which  is  sealed  so  that  the  seal  or  glass 
must  be  broken  every  time  the  release  is  used.  When 
one  has  been  broken  open  the  leverman  is  required  to 
make  a  report  of  the  circumstances.  This  has  a  ten- 
dency to  make  the  levermen  careful  to  return  the  home 
signal  levers  to  normal  as  soon  as  a  train  passes  the 
signal,  especially  as  the  hand  release  is  most  often 


IN  THEORY  AND  PRACTICE.  263 

placed  in  the  lower  story  of  the  tower,  so  that  the 
leverman  must  go  down  stairs  to  get  at  it. 

Another  quite  popular  design  is  what  is  known  as  a 
screw  hand  release.  These  are  generally  attached  to 
the  side  of  the  interlocking  machine.  They  are  operated 
by  a  long  screw  with  a  crank  on  one  end  which  takes 
about  a  half  minute  to  screw  in  to  its  full  length. 
When  screwed  in  it  operates  a  piece  of  mechanical 
locking  so  as  to  tie  up  the  machine  and  must  be 
screwed  out  to  its  normal  position  again  before  the 
machine  is  unlocked. 

There  are  two  contact  points  in  the  hand  release, 
shown  in  the  figure  on  page  261.,  as  f  and  g.  The 
former  is  closed  when  the  hand  release  is  normal  and 
the  latter  when  it  is  reversed.  At  all  times  only  one 
point  is  closed  and  the  other  open.  When  the  lever- 
man reverses  his  hand  release,  he  closes  contact  at  g. 
This  completes  a  circuit  from  d  to  r,  g,  s.  t,  u,  v,  c, 
through  relay  S,  energising  it.  After  it  is  once  ener- 
gised it  holds  itself  up  through  its  other  front  con- 
tact, attention  to  which  arrangement  was  called  above. 

This  is  what  is  known  as  a  stick  relay  arrange- 
ment. In  making  contact  at  g  the  leverman  has  broken 
contact  at  f,  which  is  in  the  electric  lock  circuit,  and, 
therefore,  the  electric  lock  F  does  not  pick  up  until 
the  hand  release  is  returned  to  normal. 

In  case  a  leverman  sets  up  a  route  for  a  train  by 
mistake,  and  then  wishes  to  change  it,  he  must  resort 
to  the  use  of  the  hand  release,  as  above,  in  order  to 
unlock  himself. 

Another  popular  form  of  electric  locking  is  to  use 
a  so-called  interlocking  relay  in  the  circuit. 

An  interlocking  relay  is  one  which  has  two  sets  of 
coils,  being  in  reality  a  double  relay.  The  armatures 
are  so  interlocked  with  each  other  (hence  the  name), 
that  whichever  of  them  drops  first  will  mechanically 
hold  up  the  other,  even  after  its  coil  is  de-energised. 


264  EAILWAT  SIGNALING 

Two  interlocking  relays  are  used  at  a  plain  cross- 
ing, one  for  each  line,  and  each  line  is  divided  into  two 
sections  ending  at  the  crossing,  each  with  its  own  track 
battery,  usually  placed  beyond  the  distant  signals.  One 
coil  of  the  interlocking  relays  acts  as  track  relay  for 
one  section  and  the  other  as  track  relay  for  the  other 
section.  As  soon  as  a  pair  of  wheels  passes  the  bat- 
tery end  of  the  section,  most  often  five  hundred  feet 
beyond  the  distant  signal,  the  side  of  the  interlocking 
relay  connected  to  that  section  drops. 

This  breaks  the  lock  circuit  and  locks  the  derail 
lever.  As  soon  as  the  first  truck  passes  over  the  cross- 
ing, the  other  side  of  the  relay  becomes  de-energised, 
but  its  armature  cannot  drop  because  the  armature  of 
the  other  magnet  holds  it  up.  As  the  last  truck  passes 
out  of  the  section  on  the  approaching  side  of  the  cross- 
ing, that  side  of  the  relay  picks  up  again,  but  its  arma- 
ture still  interlocks  that  of  the  other  side  holding  it  up. 
This  closes  the  lock  circuit  as  soon  as  the  rear  of  the 
train  is  over  the  crossing  and  releases  the  leverman 
without  making  him  wait  until  the  rear  of  the  train 
has  passed  beyond  the  distant  signal  on  the  far  side  of 
the  crossing.  Hand  releases  are  not  generally  used 
with  this  arrangement,  although  they  are  sometimes 
put  in.  In  such  an  arrangement  the  track  circuit  is 
usually  looped  through  a  circuit  breaker  attached  to 
the  arm  plate  of  the  distant  signal,  so  arranged  that 
when  the  signal  is  set  at  clear  the  corresponding  mag- 
net in  the  interlocking  relay  is  de-energised  just  as  if 
a  pair  of  wheels  had  entered  the  section.  In  this  case 
setting  the  distant  signal  at  normal  before  a  train  has 
entered  the  section  causes  the  interlocking  relay  to 
pick  up  again  and  energises  the  lock. 

Fig.  117  illustrates  a  single  track  crossing  with  an 
interlocking  relay  arrangement  as  described  for  the 
electric  locks. 

Where  power  distant  signals  are  used,  the  same  cir- 


IN  THEOKY  AND  PEACTICE. 


265 


cttit  which  is  used  for  the  back  lock  may  also  be  used 

for  the  electric  locking,  by  putting  in  a  track  circuit. 

An  arrangement  of  this  sort  is  shown  in  Fig.  118. 

The  operation  of  this  arrangement  is  as  follows: 

The  leverman,  of  course,  first  reverses  the  derail 


Track  Batteries  5oo' beyond  DisF.Sig. 


Fig.  117. 

lever,  next  the  home  signal  lever  shown  as  No.  2,  in 
the  figure,  and  lastly  the  distant  signal  lever  shown 
as  No.  i. 

What  we  wish  to  accomplish  is  this: 

(1)  Whenever  the  power  distant  signal  is  reversed 
the  home  signal  lever  must  be  locked  half  reversed. 

(2)  Whenever  a  route  has  been  set  up  in  error  it 
cannot  be  changed  unless,  either  a  train  has  passed 
through  the  track  section,  or  the  leverman  has  resorted 
to  the  use  of  the  hand  release. 

(3)  Whenever  a  pair  of  wheels  is  in  the  track  cir- 
cuit, which  in  this  arrangement  extends  between  the 
derails,  the  lock  to  be  de-energised  locking  the  home 
signal  lever  half  reversed  even  after  the  distant  signal 
is  returned  to  normal.     But  after  the  pair  of  wheels 
has  passed  out  of  the  circuit,  the  lock  to  pick  up  so 
that  the  home  signal  may  be  restored  to  normal,  thus 
releasing  the  derail  lever. 


266 


RAILWAY  SIGNALING 


The  circuit  by  which  the  first  of  these  is  accom- 
plished is  as  follows: 

When  home  signal  No.  2  is  reversed,  circuit  con- 
trollers A,  which  is  on  the  machine,  and  B,  which  is 
attached  to  the  arm  plate  of  the  signal,  are  closed,  and 
when  distant  signal  No.  I  is  reversed  circuit  controller 
shown  as  C  is  closed.  Current  then  flows  from  the 

local  battery  in  the  tower  along  wire  a  a  a  a  a, 

through  relay  R,  which  is  the  control  relay  at  the 
signal,  to  the  common  wire  and  back  to  battery. 


0>Locte  Lever  N°- 
Lever  Me***     ^Reversed 


Common  Wire 
Fig.  118. 


a    d 


This  energises  relay  R,  which  picks  up  and  closes 
circuit  from  the  local  signal  battery  through  signal 
motor  M,  which  revolves  and  clears  the  signal. 

All  this  time  the  electric  lock  D,  which  does  not  pre- 
vent the  lever  from  being  reversed,  is  down,  so  that 
when  the  home  signal  lever  is  reversed,  it  cannot  be 
set  normal  again;  thus  the  back  locking  is  accom- 
plished and  more  than  accomplished,  as  even  if  the 
distant  signal  is  set  normal  again  it  will  not  release  the 
home  signal  without  the  use  of  hand  release  E. 

By  reversing  this  hand  release  so  as  to  make  con- 
tact between  points  b  b,  current  will  flow  from  the 
local  signal  battery  along  wire  c  c  c  -  c,  through 
circuit  controller  F,  which  is  attached  to  the  arm  plate 
of  the  distant  signal  and  which,  it  should  be  noted,  is 


IN  THEOBY  AND  PBACTICE.  267 

only  closed  when  that  signal  blade  is  normal,  to  hand 
release  E  across  b  b,  through  the  electric  lock  and  back 
to  common  via  d  d. 

Now  for  our  third  problem.  The  route  being  set  up 
a  pair  of  wheels  passes  the  home  signal  and  the  track 
relay  drops.  This  closes  circuit  from  the  local  battery 
in  the  tower  through  stick  relay  S,  by  way  of  e  e  e 

e,  and  back  to  common.  Stick  relay  S  therefore 

picks  up  closing  front  contact  point  f,  so  that  as  soon 
as  the  train  passes  out  at  the  other  end  of  the  track 
circuit  and  the  track  relay  picks  up  circuit  from  the 
battery  at  the  distant  signal  through  cccccccc 
g  §T  g  S  is  closed  through  the  lock  magnet,  releasing 
lever  No.  2,  which  can  be  then  set  normal,  breaking 
circuit  through  the  stick  relay  at  circuit  controller  A, 
and  everything  is  restored  to  normal. 

Although  I  have  referred  only  to  crossings  in  this 
description  of  the  application  of  time  and  electric 
locking  to  interlocking  plants,  what  I  have  said  may 
equally  well  be  applied  to  junctions,  crossovers  or 
switches. 

One  use  of  electric  locking  which  has  come  quite 
prominently  into  vogue  of  late  years  is  as  a  substi- 
tute for  detector  bars. 

Rail  of  large  section,  100  pounds  per  yard  or  over, 
has  such  a  wide  head  that  mechanical  detector  bars, 
especially  if  link  clips  are  used,  cannot  be  depended 
on  to  strike  the  tread  of  a  wheel  which  is  over  the 
bar.  Where  such  rail  is  used  short  track  circuits, 
generally  100  feet  long,  are  put  in  at  derails  and 
switches  and  electric  locks  applied.  There  is  no  essen- 
tial difference  between  their  application  for  that  pur- 
pose and  for  any  other.  Neither  is  there  any  essential 
difference  when  electric  locking,  as  is  frequently  done, 
is  applied  to  a  power  interlocking  plant.  The  locks 
themselves,  as  before  explained,  are  made  in  a  variety 


268  RAILWAY  SIGNALING 

of  ways.  Some  fit  better  to  Saxby  and  Farmer  lock- 
ing and  some  to  vertical  locking. 

Each  relay  or  magnet  coil  of  any  sort  in  a  line 
wire  should  be  protected  by  what  are  known  as  light- 
ning arresters,  one  in  each  wire  connecting  with  the 
coil,  placed  near  the  magnet. 

There  are  many  forms  of  these  devices.  The  prin- 
ciple on  which  they  operate  is  to  have  the  operating 
circuit,  by  being  carried  through  them,  placed  so 
close  to  a  low  resistance  point  or  collection  of  points 
which  is  connected  with  the  earth,  that  in  case  of  a 
very  heavy  static  charge  being  collected  in  the  line 
wire  it  will  jump  the  gap  between  the  regular  circuit 
and  the  points  and  find  its  way  to  earth  without 
passing  through  the  magnet  coils  and  burning  them 
up.  The  regular  operating  current  being  of  too  low 
pressure  to  jump  the  gap,  no  interference  therewith 
is  effected  by  the  lightning  arrester  under  normal 
conditions. 

The  side  of  the  lightning  arrester,  which  is  con- 
nected to  earth,  should  be  attached  to  a  heavy  copper 
wire,  No.  8  at  least,  which  in  turn  should  be  securely 
fastened  to  a  ground  rod  driven  deep  enough  into  the 
ground  to  insure  contact  with  permanently  damp 
earth.  Sometimes,  where  grounds  are  particularly 
hard  to  get,  it  is  necessary  to  bury  a  copper  plate 
for  this  purpose. 

There  are  a  great  many  places  on  every  railroad 
where  there  are  outlying  switches,  or  crossovers  at 
which  it  would  be  impossible  to  put  in  complete  inter- 
locking plants,  but  which  are  so  situated  that  they 
need  more  protection  than  can  be  given  by  an  ordinary 
switch  target. 

Very  efficient  protection  may  be  had  at  such  places 
by  putting  up  signals  operated  by  a  lever  stand  and 
interlocked  with  the  switch  in  such  a  way  that  unless 
the  switch  is  set  in  the  proper  position  for  the  main 
line  the  signals  must  be  at  caution  or  danger.  Gen- 


IN  THEOKY  AND  PRACTICE. 


Fig.  119. 


270  RAILWAY  SIGNALING 

erally  it  is  sufficient  to  put  in  a  distant  (caution)  signal 
only  and  to  depend  on  the  switch  target  for  a  home 
signal,  but  in  other  cases,  especially  at  trailing  point 
crossovers,  it  is  as  well  to  put  up  both  home  and  dis- 
tant signals  and  to  dispense  with  the  switch  target 
and  lamp. 

The  interlocking  may  be  accomplished  by  using  a 
common  bolt  lock  or  by  equipping  the  switch  with  a 
facing  point  lock,  the  plunger  of  which  is  attached  to 
the  lever  which  operates  the  signal,  as  shown  in  detail 
in  Fig.  119. 

Lever  'srarid 


FPL 
Lever  Stand 

L ever  Stand 


Fig.  120. 

In  such  cases  the  signals  stand  normally  at  clear. 
The  switches  are  operated  by  the  ordinary  switch 
stand,  but  on  account  of  the  interlocking  the  signals 
must  be  set  at  caution  and  danger  before  the  switch 
can  be  thrown. 

Fig.  1 20  shows  a  facing  point  switch  and  a  trailing 
point  crossover  so  protected. 

Such  arrangements  are  frequently  used  on  the  rail- 
roads of  Continental  Europe,  and  a  report  bearing 
on  them,  issued  by  a  committee  of  the  International 
Railway  Congress  a  few  years  ago,  is  very  interest- 
ing reading.  They  are  not,  of  course,  to  be  classed 
with  complete  interlocking,  but  nevertheless  a  great 
deal  of  security  may  be  had  for  very  little  money  by 
their  use.  The  signals  are  most  frequently  wire  con- 
nected. Electric  signals,  operated  much  as  power 
distant  signals  are,  may,  however,  be  used,  a  circuit 


IN  THEORY  AND  PRACTICE.  271 

controller  being  attached  to  the  lever  by  which  the 
facing  point  lock  is  operated. 

With  such  arrangements  trains  using  the  switch  or 
crossover  must  pass  the  signals  at  stop  or  caution, 
which  by  some  is  considered  bad  practice,  but  as  a 
trainman  is  at  the  switch  to  give  hand  signals  when 
such  movements  are  to  be  made,  this  objection  does 
not  apparently  carry  much  weight,  and  where  no 
home  signal  is  used  is  unworthy  of  any  consideration 
whatever. 


CHAPTER  XVni. 

NIGHT    INDICATIONS  —  MANUAL    BLOCKING  —  CON- 
TROLLED MANUAL  BLOCKING ELECTRIC 

SLOTS. 

We  next  come  to  the  question  of  night  indications. 
This  is  one  of  the  most,  if  not  the  most,  vexatious 
problems  with  which  the  signal  engineer  is  con- 
fronted. During  the  hours  of  daylight,  the  semaphore 
makes  an  ideal  position  signal,  but  as  soon  as  dark- 
ness closes  in  we  have  to  give  up  the  position  and 
fall  back  on  a  color  indication. 

The  only  really  satisfactory  lights  which  can  be 
seen  and  distinguished  at  any  great  distance  are  red, 
green  and  so-called  white.  As  the  white  light  is  in  use 
for  every  sort  of  illuminating  purpose  at  night,  both 
on  and  off  railroads,  its  use  for  railroad  signaling  is 
objectionable.  It  is  considered  absolutely  necessary 
that  we  give  three  indications: 

Proceed  without  limitation. 

Proceed  cautiously. 

Stop. 

From  time  immemorial  a  red  light  has  been  used  as 
a  stop  signal  on  railroads.  In  England,  from  the 
earliest,  green  was  adopted  for  clear,  and  English 
railroads  have  simply  done  without  a  night  caution 
indication  (their  distant  signals  showing  red  in  the 
caution  position),  depending  on  their  engine  runners' 
bump  of  location  to  distinguish  a  distant  from  a  home 
signal. 

272 


IN  THEOBY  AND  PRACTICE. 


273 


Quite  a  number  of  years  ago  the  Chicago  &  North- 
western Railway  adopted  green  for  clear,  and,  in 
default  of  anything  better,  uses  a  double  light  red 
and  green  side  by  side  for  a  caution  indication.  Up 
until  this  step  was  made  by  the  Northwestern,  it  had 
been  the  universal  practice  in  this  country  to  use 
white  lights  for  clear  and  green  for  caution.  This 
practice  was  continued  by  most  railroads  for  some 
time,  but  within  the  past  five  years  many  of  them 
have  adopted  green  for  clear  and  an  orange  yellow 
for  caution. 


-I 


Fig.  121. 


This  latter  appears  to  be  the  best  single  light  yet 
proposed,  but  still  it  is  far  from  being  as  distinct  a 
color  as  either  red  or  green. 

A  very  serious  objection  to  the  use  of  white  for 
clear  is  that  as  the  lamp  itself  gives  out  a  white  light, 
this  will  show  through  the  arm  plate  if  a  colored 
roundel  should  be  broken  out,  so  that  a  clear  signal 
may  appear  to  an  engine  runner  when  a  stop  or  cau- 
tion signal  is  intended.  It  is  remarkable  that  accidents 


274 


EAILWAY  SIGNALING 


do  not  happen  from  this  cause  more  frequently  than 
they  do. 

The  almost  universal  type  of  semaphore  lamp  is 
shown  in  Fig.  121.  This  has  an  uncolored  glass  mag- 
nifying lens  through  which  the  light  from  an  oil  or 
incandescent  lamp  shows  in  its  front.  This  lens  is 
5%  inches  in  diameter.  A  plain  bull's  eye  about  two 
inches  in  diameter  is  most  frequently  placed  in  the 
back  of  the  lamp.  The  focal  point  of  the  front  lens 
is  arranged  to  fall  in  the  flame  of  the  lamp.  A 


Lamp 
/Spectacle 


Fig.  122. 

bracket  or  hook  is  attached  to  the  side  of  the  sema- 
phore pole  near  the  top  and  a  sleeve  in  the  side  of 
the  lamp  fits  over  this  hook,  holding  the  lamp  in 
place. 

The  semaphore  arm  plate  has  plain  colored  glass 
called  roundels  let  into  it,  which  are  moved  in  front 
of  or  away  from  the  lens  in  the  lamp  as  the  arm 
plate  changes  its  position.  For  instance,  a  home  sig- 


IN  THEORY  AND  PRACTICE.  275 

nal  with  the  blade  horizontal  will  have  a  red  roundel 
in  front  of  the  lens.  If  green  is  the  color  for  a  clear 
indication  a  green  roundel  will  be  moved  in  front 
of  the  lamp  when  the  arm  plate  assumes  the  clear 
position.  If  white  is  used  for  clear,  no  roundel  is 
brought  before  the  lens  in  the  clear  position  of  the 
arm  plate,  and  the  lens  of  the  lamp  itself  gives  the 
clear  indication. 

A  glance  at  Fig.  122  will  serve  to  make  this  de- 
scription clearer. 

Sometimes  what  is  known  as  a  continuous  light 
arm  plate  is  used.  This  is  shown  in  Fig.  122.  It 
will  be  noticed  that  there  are  two  red  and  one  green 
roundels  in  this  casting.  The  object  of  this  is  to 
have  the  signal  show  red  until  it  is  in  the  full  clear 
position.  In  case  the  connections  are  loose  and 
the  blade  droops,  the  signal  will  not  give  a  false  clear 
indication. 

The  back  light  is  used  so  that  the  leverman  in  the 
tower  may  be  able  to  tell  whether  or  not  the  lamps 
in  signals  which  face  away  from  him  are  burning, 
and  whether  the  signals  respond  to  the  movement  of 
the  levers.  A  small  attachment  called  the  back  light 
casting,  of  which  mention  has  already  been  made,  is 
attached  to  the  spindle  and  works  behind  the  lamp. 
This  carries  a  small  roundel,  usually  purple  or  blue, 
through  which  the  light  shows  when  the  signal  is 
normal ;  the  white  bull's  eye  showing  when  the  signal 
is  reversed.  Signals  which  face  the  tower,  and  those 
which  cannot  be  seen  from  the  tower  should  have  the 
back  lights  blinded  by  soldering  a  piece  of  tin  over 
the  bull's  eye,  or  painting  it  over  on  the  inside  of  the 
lamp. 

Fig.  123  shows  one  of  the  Chicago  &  North  west- 
ern's caution  signal  lamps.  In  the  back  of  the  exten- 
sion is  a  looking-glass  reflector  which  throws  the  light 
from  the  burner  through  the  plain  green  glass.  The 


276 


KAILJTAY  SIGNALING 


lamp  proper  is  fitted  with  a  red  lens  instead  of  a 
white  one.  No  roundels  are  used  in  the  arm  plate. 
When  in  the  horizontal  position  the  red  lens  is  ex- 
posed to  view.  When  in  the  clear  position  a  metal 


£_-          __/^_". J 


disc  is  moved  before  it  so  as  to  obscure  it,  leaving 
the  green  light  alone  visible.  One  burner  is  used  so 
that  in  case  the  lamp  should  go  out,  both  lights  will 
be  extinguished.  If  two  separate  burners  were  used, 


OF 


IN  THEORY  AND  PRACTICE.  277 

the  one  in  the  red  lamp  might  go  out,  leaving  the 
green  light  showing,  which  would  give  a  clear  instead 
of  a  caution  indication,  as  intended. 

So  far  we  have  had  in  mind  two  position  signals 
only.  Three  position  signals  usually  show  a  red  light 
at  horizontal,  a  green  or  yellow  light  at  inclined  45 
degrees,  and  a  white  or  green  light  when  vertical. 
This  is  determined  by  the  shape  of  the  arm  plate,  and 
there  is  no  difference  worthy  of  note  between  them 
and  the  two  position,  so  far  as  the  operating  mech- 
anism is  concerned. 

One  serious  objection  to  the  present  system  of  night 
indications  is  that  men  whose  vision  is  affected  by 
color  blindness  are  apt  to  make  mistakes  in  reading 
the  colors.  Any  man  whose  range  of  vision  is  normal 
can  see  the  positions  of  a  semaphore  blade  in  day- 
light, even  though  he  may  not  be  able  to  distinguish 
red  from  green,  or  vice  versa,  at  night.  Efforts  have 
been  made  from  time  to  time  to  develop  an  illumi- 
nated semaphore  blade,  but  it  cannot  be  said  that  up 
to  the  present  they  have  been  crowned  with  any  suc- 
cess. It  is  a  fact  that  I  have  noticed  in  riding  on 
engines  at  night,  that  where  powerful  electric  or 
acetylene  headlights  are  used,  it  is  often  possible  to 
see  the  position  of  semaphore  blades  as  distinctly  as 
in  daylight,  and  it  may  be  that  some  special  design 
of  headlight  may  yet  be  attempted  for  this  purpose. 

A  great  deal  of  attention  was  attracted  some  years 
ago  to  the  so-called  long  time  burner.  This  is  a 
burner  designed  to  be  used  in  a  kerosene  lamp,  which 
consumes  so  little  oil  that  it  may  be  left  burning  for 
several  days  without  any  attention,  and  yet  will  give 
out  sufficient  light  for  a  signal  lamp.  The  first  enthu- 
siasts claimed  a  little  too  much  for  these  burners,  de- 
claring they  did  not  need  attention  for  a  week  at  a 
time.  This  did  not  work  out  in  practice,  and  a  reac- 
tionary feeling  was  developed  against  them,  which 


278  -RAILWAY  SIGNALING 

went  as  far  in  the  other  direction.  My  experience  has 
been  that  where  they  are  looked  after  and  the  crust 
removed  from  the  wick  every  second  day,  they  will 
give  very  good  results. 

Some  attempts  have  been  made,  with  more  or  less 
success,  to  light  signal  lamps  by  acetylene  or  ordinary 
illuminating  gas.  The  latter  is  frequently  done  abroad. 

The  American  Railway  Association  has  defined  a 
block  as  being  "a  length  of  track  of  defined  limits, 
the  use  of  which  by  trains  is  controlled  by  block 
signals." 

A  block  signal  is  one  used  solely  to  warn  a  train 
that  it  is  safe  or  unsafe  for  it  to  proceed  into  the 
block  which  that  signal  governs.  There  is  a  general 
tendency  to  use  semaphore  signals  of  much  the  same 
design  as  those  used  for  route  signalling  as  block 
signals,  although  flags,  discs  and  hand  lanterns  are 
occasionally  used. 

The  simplest  form  of  blocking  now  used  in  this 
country  is  the  so-called  Telegraph  Block. 

We  have,  we  will  say,  two  stations,  A  and  B.  They 
are  in  communication  with  each  other,  either  by  tele- 
graph, telephone  or  electric  bells.  A  train  comes  up 
to  A,  moving  in  the  direction  of  B.  The  operator 
at  A  signals  the  operator  at  B  that  he  has  a  train 
he  wishes  to  admit  into  the  block ;  B  signals  back  his 
acquiescence,  and  A  admits  the  train  either  by  clear- 
ing a  signal,  notifying  the  train  crew  verbally,  or  in 
writing,  or  by  some  other  means.  Now  until  that 
train  reaches  B,  the  operator  there  is  supposed  to  hold 
his  signal  for  a  movement  from  B  towards  A  at  stop, 
and  to  clear  it  for  nobody  (we  are  supposing  a  single 
track  line)  until  the  train  which  A  operator  has  ad- 
mitted has  passed  B.  A  in  the  meantime  sets  his  sig- 
nal at  stop  behind  the  train  and  will  not  clear  it  again 
without  B's  permission.  If  B  wants  to  admit  a  train 
from  his  end  he  has  to  get  A's  permission. 


IN  THEORY  AND  PRACTICE.  279 

Now,  this  is  all  very  easy  and  simple,  and  as  long 
as  nobody  makes  a  mistake  trains  may  be  moved  with 
perfect  safety  and  with  great  dispatch  in  that  way, 
provided  they  have  a  chance  to  pass  each  other  when 
they  meet.  But  if  B  forgets  about  having  let  A 
admit  a  train  and  lets  one  in  from  his  end,  or  if  A 
forgets  to  restore  his  signal  to  stop  and  then  goes 
to  sleep  or  drops  dead,  and  if  the  train  he  had  ad- 
mitted should  be  forced  to  stop  in  the  block  and 
another  one  following  it  should  find  the  clear  signal 
at  A  and  go  on,  very  serious  consequences  may 
result. 

However,  the  ordinary  manual  block  system  is  just 
exactly  what  has  been  described,  and  it  has  done  and 
is  doing  good  work  every  day  on  thousands  of  miles 
of  American  railroad. 

Where  only  one  train  is  allowed  in  a  block  at  one 
time,  it  is  known  as  absolute  blocking. 

It  is,  however,  more  frequently  the  rule  than  not, 
at  least  as  regards  freight  trains,  to  allow  one  train 
to  follow  another  into  a  long  block  before  the  first 
one  has  been  reported  out  at  the  other  end,  the  crew 
of  the  second  train  being  warned  before  entering  the 
block  that  there  is  another  train  ahead  of  them.  Where 
this  is  done,  it  is  known  as  permissive  blocking. 

As  before  stated,  semaphore  signals  are  most  fre- 
quently used  for  manual  block  signals. 

Some  roads  distinguish  their  block  semaphore  sig- 
nals from  their  route  signals  by  sawing  off  the  cor- 
ners of  the  blade  at  the  end  farthest  from  the  mast,  so 
as  to  point  the  blade;  some  paint  them  differently 
from  route  signal  blades,  and  some  make  no  distinc- 
tion between  them. 

In  American  practice  the  ordinary  commercial  sta- 
tions are  used  as  block  stations,  as  well.  The  opera- 
tors usually  have  a  room  with  a  bay  window  extend- 
ing out  into  the  platform,  so  that  they  can  see  up 


280 


RAILWAY  SIGNALING 


and  down  the  track.  The  semaphore  is  usually  placed 
in  the  platform  just  outside  of  the  bay  window,  or  if 
the  view  is  obstructed  by  water  tanks,  elevators  or 
trees,  it  is  often  placed  across  the  track.  Semaphores 


Fig.  124. 


used  for  such  purposes  most  frequently  have  two 
blades,  one  to  govern  the  block  at  one  side  of  the  sta- 
tion, and  one  to  govern  the  block  on  the  other  side. 


IN  THEORY  AND  PEACTICE.  281 

See  Fig.  124  for  a  typical  illustration  of  such  a 
signal. 

These  signals  are  sometimes  wire  connected  and 
sometimes  pipe  connected.  The  best  practice  is  to 
pipe  connect  them,  as  they  are  very  important  signals. 
Levers  of  some  sort  are  placed  in  the  operator's  room, 
so  as  to  be  easily  within  his  reach,  by  which  the  blades 
are  operated.  There  is  no  uniformity  of  practice  as  to 
the  construction  of  these  levers.  A  great  many  rail- 
roads make  them  in  their  own  shops,  and  every  imag- 
inable design  of  wheel  pulley  and  lever  are  to  be  found 
in  use. 

Where  a  semaphore  signal  such  as  described  is  used, 
the  arm  plates  are  so  arranged  that  only  one  lamp  is 
necessary.  This  is  in  all  essentials  the  same  as  the 
lamp  just  described,  except  that  it  has  two  5^ -inch 
lenses  opposite  each  other,  instead  of  one  lens  and  a 
small  bull's  eye. 

Manual  block  signals  are,  like  route  signals,  kept 
normally  at  stop  and  cleared  only  to  allow  a  train  to 
pass. 

Where  permissive  blocking  is  in  use,  crews  of  fol- 
lowing trains  are  given  warning  that  another  train 
is  in  the  block  ahead  of  them  by  signal  or  by  the  use 
of  so-called  caution  cards. 

There  is  not  much  uniformity  in  the  signals  used. 
One  large  company  uses  a  three  position  signal,  in 
which  the  blade  at  stop  is  in  the  horizontal  position, 
at  clear  is  inclined  downward  45  degrees,  and  at  cau- 
tion is  inclined  upward  45  degrees. 

Another  company  uses  a  home  and  distant  signal 
on  the  same  mast,  home  above  and  distant  below.  Both 
inclined  downward  at  60  degrees  indicates  that  the 
block  is  clear.  Both  horizontal  indicates  stop,  and  the 
upper  blade  inclined  downward  with  the  lower  one 
horizontal  indicates  that  a  train  may  enter  the  block 
permissively. 


282  EAILWAY  SIGNALING 

The  American  Railway  Association  has  recom- 
mended a  standard  form  of  caution  card  which  is  very 
generally  used,  so  that  as  far  as  the  use  of  caution 
cards  is  concerned,  practice  may  be  said  to  be  uniform. 

In  the  ordinary  telegraph  block  which  we  have  just 
been  discussing,  there  is  no  surety  that  A  will  ask 
B  for  permission  to  admit  a  train  or  that  B  will  not 


Fig.  125. 


admit  a  train  from  his  end  after  A  has  admitted  one 
from  his.  Mistakes  of  this  sort  have  been  made 
and  have  been  the  cause  of  some  very  costly  acci- 
dents. This  brought  out  the  idea  of  electrically  con- 
necting A  and  B  in  such  a  way  that  A  could  not  clear 
his  signal  unless  B  first  unlocked  it  for  him.  Such  an 
arrangement  is  known  as  the  controlled  manual  block. 
There  are  several  sorts  of  apparatus  designed  for 


IN  THEORY  AND  PEACTICE.  283 

this  purpose  on  the  market,  any  one  of  which  will 
accomplish  the  desired  result.  Fig.  12$  shows  a  very 
popular  type  of  instrument  gotten  out  by  the  General 
Railway  Signal  Company.  The  cranks  act  as  levers 
to  operate  the  signal  blades.  By  a  simple  arrange- 
ment of  electric  locks,  shown  in  the  sectional  view, 
the  crank  connected  to  A's  signal  cannot  be  moved 
unless  both  A  and  B  at  the  same  time  hold  circuit 
breakers  in  their  respective  instruments  closed. 

The  use  of  such  instruments  insures  that  the  oper- 
ators at  either  end  of  a  block  communicate  with  each 
other  before  admitting  a  train,  but  the  train  once  in, 
either  of  them  can  call  on  the  other  for  an  unlock, 
and  if  the  man  called  on  forgets  himself  and  gives 
it  may  admit  another  train.  This  is  guarded  against 
by  carrying  a  track  circuit  entirely  through  the  block 
and  cutting  the  wire  which  connects  the  two  instru- 
ments through  the  front  contact  of  the  relay  of  every 
section  in  the  block. 

Then  so  long  as  any  relay  is  down,  and  one  or 
more  must  be  down  while  there  is  a  train  in  the 
block,  the  wire  by  which  A  and  B  unlock  each  other 
is  broken  and  neither  can  unlock  the  other. 

Very  frequently  the  passing  tracks  at  stations  are 
so  long  that  their  far  ends  are  quite  a  distance  from 
the  station. 

Trains  on  passing  tracks,  waiting  to  be  passed  by 
other  trains,  have  been  known  to  pull  out  on  the  main 
track  at  the  far  end  of  the  passing  track,  when  they 
should  not,  and  thus  get  into  the  block  at  a  time 
when  the  block  operators  supposed  it  clear.  In  order 
to  put  these  switches  absolutely  under  the  control  of 
the  block  operator,  they  are  often  locked  with  elec- 
tric locks,  which  are  put  under  his  control. 

These  refinements  are  mostly  in  an  experimental 
stage  still,  and  there  is  no  uniformity  about  the  devices 
used. 


284  RAILWAY  SIGNALING 

Theoretically  no  doubt  they,  like  electric  locking  at 
interlocking,  add  greatly  to  the  safety  of  a  block 
system,  but  in  practice,  with  the  frequent  interrup- 
tions caused  by  their  getting  out  of  order,  it  is  doubt- 
ful whether  they  add  much  real  safety. 

Controlled  manual  block  is  often  called  lock  and 
block.  One  great  trouble  with  all  lock  and  block 
instruments  yet  designed  is  that  the  men  can  beat 
them  if  they  make  up  their  minds  to  do  so. 

A  great  mistake  is  always  made  if,  when  any  such 
apparatus  is  installed,  the  men  who  operate  it  are 
given  to  understand  that  the  device  cannot  be  beaten. 
This  puts  them,  many  of  them  having  unlimited  time 
at  their  disposal,  on  their  mettle  to  find  out  why  it 
cannot  be  beaten,  and  some  unrecognized  genius  is 
certain  to  discover  the  secret  sooner  or  later.  It  is 
much  better  to  tell  the  men  plainly  at  the  start  that 
the  apparatus  can  be  tampered  with  if  they  want  to, 
but  that  it  is  put  there  for  their  own  protection,  to 
prevent  their  making  hasty  mistakes,  and  they  had 
much  better  try  to  keep  it  in  good  working  order. 

A  very  simple  and  reliable  system  of  controlled 
manual  block  is  what  is  known  as  the  electric  train 
staff. 

The  present  staff  block  system  and  apparatus  is  an 
evolution  from  a  very  crude  and  very  early  block 
system. 

When  the  Stockton  &  Darlington  Railway,  which 
was  the  first  road  to  be  opened  as  a  public  commer- 
cial enterprise,  commenced  to  do  business,  it  was  soon 
found  that  trains  would  meet  each  other  between  sta- 
tions (the  line  was  single  track).  As  a  large  part  of 
the  traffic  of  this  line  was  moved  by  horses,  and  even 
when  locomotives  were  used,  their  speed  did  not  ex- 
ceed eight  miles  an  hour,  there  was  no  great  danger 
of  collision,  but  one  or  the  other  train  had  to  back 
up  until  a  passing  track  was  reached.  This  made 


IN  THEORY  AND  PEACT1CE.  285 

serious  delays,  especially  as  the  crews  of  the  meeting 
trains  usually  quarreled  as  to  which  had  the  right 
to  proceed  and  which  must  back  up.  To  overcome 
this  last  difficulty,  the  railroad  company  had  posts  put 
up  midway  between  passing  tracks.  Whichever  train 
reached  the  post  first  had  the  right  to  proceed,  and 
the  other  was  compelled  by  the  rules  to  back  up  and 
make  way  for  it.  As  speed  and  the  number  of  trains 
increased,  and  it  is  to  be  remembered  that  the  ten 
years  following  the  opening  of  the  Stockton  &  Dar- 
lington saw  wonderful  progress  in  railroad  improve- 
ment, this  arrangement  was  found  to  be  impractica- 
ble. The  next  step,  therefore,  was  to  provide  a  talis- 
man, or  sign,  the  possession  of  which  gave  the  'train 
holding  it  the  right  to  proceed,  while  all  other  trains, 
as  there  was  only  one  for  each  block,  were  forced  to 
stop  and  wait  for  the  train  having  possession  of  the 
talisman  to  pass  through  the  block.  A  staff  was  used 
for  this  purpose,  from  which  the  system  has  acquired 
its  name,  although  the  insignia  now  used  can  hardly 
be  said  to  have  the  slightest  resemblance  to  a  staff. 
As  long  as  traffic,  as  represented  by  the  number  of 
trains  on  the  road,  was  equal  in  both  directions,  and 
as  long  as  for  every  train  that  went  north  or  west 
another  train  went  east  or  south  before  there  was  a 
movement  in  either  of  the  former  directions,  this 
worked  well  enough,  because  a  train  taking  the  staff 
at  A  left  it  at  B,  and  as  the  next  movement  was  from 
B  to  A,  the  staff  was  brought  back  again.  If  several 
trains  wanted  to  move  from  A  towards  B  before 
one  moving  in  the  other  direction  appeared,  all  but 
the  first  one  had  to  wait  at  A  until  the  other  train 
came  along  and  brought  the  staff  back.  It  should 
be  remembered  that  in  these  early  days  there  was  no 
electric  telegraph,  so  that  communication  between 
stations  any  distance  apart  was  impossible,  except  by 
messenger  or  by  a  system  of  telegraphing  by  using 


286 


RAILWAY  SIGNALING 


semaphores  placed  within  sight  of  each  other,  which, 
of  course,  was  useless  in  foggy  weather. 

Various  systems  of  dividing  the  staff  into  several 
parts  and  giving  each  of  several 
trains  moving  in  the  same  direction 
a  part  of  it  were  tried  with  more  or 
less  success,  until  finally  the  use  of 
the  electric  telegraph  showed  how  it 
was  possible  to  operate  electro-mag- 
nets miles  away,  and  a  system  of  pro- 
viding a  supply  of  staffs  at  each  end 
of  the  block,  enclosed  in  cases  elec- 
trically locked  in  such  a  manner  that 
when  a  staff  was  taken  out  of  either 
case  the  cases  could  not  be  opened 
again  until  this  staff  was  returned  to 
one  or  the  other  of  them,  was 
evolved.  This  solved  the  problem 
of  irregular  movement  of  trains  so 
far  as  direction  was  concerned,  and 
it  only  remained  to  perfect  the  appa- 
ratus. Ten  or  twelve  years  ago  the 
staffs  were  a  club  of  metal  about  one 
and  a  half  inches  in  diameter  and 
two  feet  long.  Their  weight  was  so 
great  that  enough  force  was  required 
to  overcome  their  inertia  when  pick- 
ing them  up  to  make  it  dangerous 
for  men  leaning  out  of  engine  cabs 
while  the  engine  was  moving  swiftly 
to  catch  them  out  of  cranes,  and  throwing  them  off  at 
stations  where  trains  did  not  stop  was  dangerous  to 
bystanders.  The  staff  of  today  is  a  mere  round  steel 
key  of  little  larger  diameter  than  a  lead  pencil,  and 
five  or  six  inches  long. 

Fig.  126  illustrates  a  modern  staff  instrument. 
With  these  instruments,  not  only  is  it  impossible 


IN  TEEOET  AND  PRACTICE.  287 

to  take  out  a  staff  after  one  has  been  taken  out  of 
either  of  those  at  opposite  ends  of  a  block,  but  even 
when  no  staff  is  out,  A  cannot  remove  one  without 
first  getting  B  to  unlock  him,  and  vice  versa. 

In  practice  the  staffs  are  taken  out  by  the  block 
operators  and  handed  to  train  or  engine  men  as  they 
pass  the  block  station,  either  by  putting  the  staff 
in  a  leather  or  India  rubber  pouch  and  suspending  it 
from  a  crane,  something  like  a  mail  crane,  from  which 
engine  men  on  passing  trains  can  either  pick  them  off 
by  hand  or  by  a  catching  device  attached  to  the 
engine ;  or  by  handing  them  to  the  engine  men.  When 
the  latter  method  is  pursued,  the  pouch  is  generally 
made  of  rubber  hose  shaped  into  a  ring  about  two 
feet  in  diameter.  The  operator  holds  this  up  so  that 
the  engine  man  standing  in  the  gangway  or  leaning 
out  of  the  cab  window  can  pass  his  arm  through  the 
ring.  I  have  seen  them  picked  up  in  this  manner 
at  a  speed  of  forty  miles  an  hour,  and  have  ridden 
on  an  engine  by  which  one  was  picked  up,  through 
the  means  of  a  mechanical  catcher  from  a  crane, 
while  we  were  running  at  a  speed  of  sixty-three  miles 
an  hour. 

Formerly  it  was  considered  necessary  to  divide  the 
staff  and  give  part  of  it  to  the  engine  runner  and 
part  to  the  conductor,  as  a  check  on  each  other,  but 
in  the  practice  of  today  it  is  thought  sufficient  if  the 
whole  staff  is  taken  by  the  engine  runner. 

Where  staffs  are  to  be  picked  up  at  speed,  it  is 
customary  to  work  them  in  conjunction  with  a  block 
signal.  The  signal  at  proceed  means  that  there  is  a 
staff  out  ready  to  be  picked  up.  The  signal  at  stop 
means  there  is  no  staff  ready  for  the  approaching 
train,  and  it  must  stop  and  wait  until  one  is  released. 
Sometimes  as  an  extra  precaution  the  staff  itself  acts 
as  a  key  to  the  block  signal  which  cannot  be  cleared 


288  RAILWAY  SIGNALING 

until  a  staff  has  first  been  taken  from  the  case,  and 
then  used  to  unlock  the  signal  lever. 

If  there  is  a  switch  leading  into  the  main  track 
between  two  block  stations,  a  special  staff  machine 
can  be  placed  there. 

Any  train  wishing  to  enter  the  main  track  by  way 
of  the  switch  must  first  call  up  A  or  B  and  get  a 
staff  released,  which  neither  A  nor  B  can  do  if  a 
staff  is  already  out  between  them.  On  getting  the 
release  the  train  man  of  the  waiting  train  takes  out  a 
staff  which  he  uses  as  a  key  to  unlock  the  switch.  It 
must  stay  in  the  lock  until  the  switch  is  set  normal 
behind  the  train,  but  is  all  the  while  holding  A's  and 
B's  instruments  locked.  After  returning  the  switch 
to  normal,  the  train  proceeds  to  either  A  or  B,  as  the 
case  may  be,  and  on  reaching  there  delivers  the  staff 
to  the  block  operator,  who  puts  it  back  in  his  instru- 
ment, restoring  the  entire  combination  to  normal,  just 
as  if  the  staff  had  come  to  him  from  the  other  end 
of  the  block. 

A  train  entering  the  siding  would  use  the  staff 
which  A  or  B  had  given  it  to  unlock  the  switch,  after 
which,  when  the  switch  was  set  normal  again,  the 
staff  would  be  put  in  the  special  instrument  and 
everything  restored  to  normal. 

It  is  customary  to  start  out  with  an  equal  number 
of  staffs  in  each  of  the  instruments  at  either  end  of 
a  block,  but  if,  as  is  usually  the  case,  there  are  more 
trains  moving  in  one  direction  than  in  the  other, 
sooner  or  later  all  the  staffs  will  get  to  one  end  or 
the  other  of  the  block.  It  is  often  many  days,  weeks 
or  months  before  this  happens.  The  cases  may  be 
unlocked  by  the  maintainer,  who  can  take  out  staffs 
enough  to  even  things  up,  from  the  bottom  of  the 
case,  and  carry  them  to  the  other  station,  putting 
them  in  the  case  there,  without  interfering  with  the 
operation  of  the  instruments  during  this  transposition. 


IN  THEORY  AND  PEACTICE.  289 

Of  course  it  is  understood  that  the  change  will  be 
made  before  one  case  or  the  other  is  completely  ex- 
hausted, so  that  there  will  be  staffs  enough  to  con- 
duct business  while  they  are  being  moved. 

The  staffs  for  one  block  will  not  fit  in  the  instru- 
ments belonging  to  the  adjacent  blocks,  so  that  they 
can  be  used  only  between  two  given  stations.  For 
instance,  if  there  are  three  blocks,  A-B,  B-C,  C-D, 
there  will  be  one  instrument  at  A,  two  at  B,  two  at 
C,  and  one  at  D.  The  staffs  that  work  between  A 
and  B  will  be  of  a  different  shape  from  those  that 
work  between  B  and  C  or  C  and  D.  Staffs  are  cut,  I 
believe,  by  the  makers  in  about  ten  different  shapes, 
so  that  every  tenth  block  will  use  the  same  type  of 
staff.  It  is  thought  that  this  distance  is  sufficient  to 
insure  against  their  misuse. 

Besides  the  intermediate  or  junction  staff  instru- 
ments, already  alluded  to,  an  arrangement  can  be 
furnished  by  which  a  secondary  staff  may  be  taken 
out  and  given  to  a  pusher  or  helping  engine  which 
only  goes  part  way  through  the  block  and  then  returns 
to  the  initial  station. 

The  regular  staff  is  given  to  the  through  train, 
while  the  helping  engine  carries  the  secondary  staff. 
Assuming  that  the  train  starts  from  A  and  the  help- 
ing engine  cuts  off  half  way  between  A  and  B  and 
returns  to  A.  Now,  if  the  through  train  reaches  B 
and  turns  in  its  staff  before  the  helper  gets  back  to 
A,  the  block  is  still  held  by  the  helper  through  the 
medium  of  the  secondary  staff.  B  could,  of  course, 
keep  the  staff  which  was  turned  in  to  him  by  the 
through  train  without  returning  it  to  its  case,  and  give 
it  to  some  train  going  towards  A,  but  it  is  unlikely 
that  he  would  do  so  in  the  first  place,  and  in  the 
second  place  the  train  would  be  following  the  helper 
and  would  be  very  unlikely  to  overtake  it  before  it 
reached  A.  In  case  the  helper  arrived  back  at  A 


290  RAILWAY  SIGNALING 

before  the  through  train  reached  B,  the  staff  carried 
by  the  through  train  would  hold  the  block  even  after 
the  secondary  staff  was  turned  in  by  the  helping  engine 
at  A  and  deposited  in  its  case. 

Further  than  this,  in  order  to  allow  permissive 
movements  of  trains,  the  staff  can  be  arranged  as  a 
key  to  a  box  containing  a  certain  number  of  tablets. 
If  it  is  desired,  for  instance,  to  let  three  trains  move 
from  A  to  B  at  intervals  of  only  a  few  minutes  apart, 
without  allowing  any  train  to  move  from  B  towards 
A  in  the  meantime,  A  calls  on  B  for  an  unlock,  and 
when  he  gets  it  he  takes  a  staff  out  of  his  machine. 

This  effectually  ties  up  B.  A  then  takes  the  staff 
and  unlocks  the  tablet  box  with  it.  The  lock  of  this 
box  is  so  arranged  that  the  staff  cannot  be  removed 
from  the  lock  until  all  of  the  tablets  have  been  re- 
moved. After  unlocking  the  tablet  box,  A  takes  out 
the  first  tablet  and  gives  it  to  the  first  train.  This 
authorizes  it  to  proceed  exactly  as  a  staff  does.  Then 
he  takes  out  the  second  tablet  and  gives  that  to  the 
second  train.  Then  he  takes  out  all  the  remaining 
tablets  and  the  staff,  which  he  gives  to  the  third  train. 
The  removal  of  one  or  more  tablets  from  the  box  has 
the  same  effect  as  the  taking  out  of  a  staff,  so  that  in 
case  A  took  out  all  the  tablets  the  first  time,  his  and 
B's  instruments  would  remain  locked  just  the  same. 

From  the  foregoing  the  reader  will  see  that  the 
staff  system  can  be  applied  so  as  to  cover  almost  any 
contingency  which  can  arise  in  the  blocking  of  trains, 
and  yet  for  some  reason  which  I  could  never  fathom 
its  use  does  not  appear  to  appeal  to  American  operat- 
ing railway  men.  It  is  in  general  use  in  Great  Britain 
and  the  English  Colonies,  except,  I  believe,  in  Canada, 
for  single  track  blocking.  Its  operation  is  simplicity 
itself,  and  it  is  without  question  the  safest  single  track 
block  arrangement  known  to  man.  In  the  United 
States  its  use  is  confined  almost  entirely  to  protecting 


IN  THEORY  AND  PRACTICE.  291 

dangerous  blocks,  like  those  including  tunnels,  single 
track  bridges,  gauntlets,  or  short  pieces  of  single 
track  connecting  two  double  track  lines. 

The  Southern  Pacific  Railway  Company  has  over 
one  hundred  miles  of  line  blocked  in  this  way.  Its 
performance,  I  am  informed,  is  very  satisfactory,  but 
this,  as  far  as  I  am  aware,  is  the  only  case  in  this 
country  where  it  is  used,  except,  as  above  noted,  to 
protect  particularly  dangerous  isolated  spots. 

The  cost  of  an  installation,  although  not  equal  to 
that  of  automatic  signals,  is  still  considerable,  espe- 
cially if  semaphore  signals  and  staff  cranes  have  to 
be  provided.  This  may  be  one  reason  why  its  use  is 
not  more  general  in  this  country.  Another  reason 
may  be  that  as  a  great  deal  of  American  railroad  car- 
ries a  fluctuating  amount  of  traffic,  stations  are  closed 
at  certain  seasons  of  the  year  and  opened  at  others. 
Since  the  passage  by  Congress  of  the  so-called  "nine- 
hour  law,"  by  which  railroads  are  forbidden  to  allow 
block  operators  to  work  more  than  nine  hours  out 
of  twenty-four,  it  is  quite  common  to  close  certain 
block  stations  one  trick  of  from  six  to  eight  hours 
each  day.  The  staff  does  not  lend  itself  very  readily 
to  such  an  arrangement.  It  can  be  done  as  follows, 
but  this  means  a  good  deal  of  extra  apparatus.  Sup- 
pose there  are  three  stations,  A,  B  and  C,  and  it  is 
desired  to  cut  B  out  from  12  o'clock  midnight  until 
6  o'clock  in  the  morning,  an  additional  instrument 
may  be  put  at  A  and  one  at  C,  using  a  staff  different 
from  those  used  between  A,  B  and  C  when  B  is  in 
service.  It  is  not  necessary  to  string  additional  line 
wires,  as  an  arrangement  of  electric  switches  can  be 
put  in  by  which  B  on  going  off  duty  will  cut  out  his 
instrument  and  connect  the  line  through  his  station; 
A  and  C  by  throwing  switches  will  cut  out  their  in- 
struments which  work  with  B  and  cut  in  the  two  extra 


292  RAILWAY  SIGNALING 

instruments.  This  arrangement  prevents  them  for- 
getting to  cut  B  in  again  when  he  comes  to  work  next 
morning,  as  they  might  do  if  they  had  a  separate 
circuit  of  their  own,  because  B  will  cut  himself  in, 
which  will  disconnect  the  extra  instruments  at  A 
and  C. 

Lock  and  block  instruments  and  staff  instruments 
as  well  can  be  operated  for  short  blocks  on  what  is 
known  as  a  grounded  circuit ;  that  is,  instead  of  having 
two  wires  between  the  instruments,  one  to  carry  the 
current  out  and  one  to  bring  it  back  again,  one  wire 
may  be  used,  the  other  side  of  the  magnets  being  con- 
nected to  the  earth.  In  this  way  the  earth  acts  as  a 
common  wire.  A  telephone,  too,  may  be  put  in,  using 
the  same  wire  which  is  used  for  the  control  wire  of 
the  lock  and  block  or  staff.  This  saves  a  great  deal 
of  wire  and  consequently  reduces  the  expense  of  an 
installation.  What  are  known  as  dry  battery  cells, 
too,  may  be  used.  These  are  cells  in  which  the  elec- 
trolyte is  made  into  a  stiff  paste  so  that  it  will  not 
spill  out.  These  cells  are  convenient  to  handle  and 
do  not  require  much  room.  They  have  a  high  voltage 
also.  Their  life,  however,  is  less  certain  than  that  of 
a  Lalande  cell,  and  cells  may  fail  at  unexpected  times. 
The  first  cost  of  dry  cells  is  much  less  than  that  of 
Lalande  cells,  but  as  they  cannot  be  renewed,  there  is 
no  great  economy  in  their  use.  The  only  advantage 
is,  as  before  stated,  in  the  fact  that  they  are  clean  to 
handle  and  require  very  little  space  to  be  "set  up"  in. 

A  use  to  which  track  circuits  are  sometimes  put  is 
to  operate  semi-automatic  signals.  What  are  known 
as  electric  slots  are  applied  to  mechanical  signals  for 
this  purpose.  Two  sorts  of  slots  are  in  general  use. 
One  known  as  a  spindle  slot  is  attached  to  the  spindle 
of  a  mechanical  signal.  The  slot  contains  an  arrange- 
ment of  electro-magnets  energized  by  a  local  battery 
working  through  the  track  relay  which  when  ener- 


IN  THEOEY  AND  PRACTICE.  293 

gized  holds  the  arm  plate  tight  to  the  spindle,  so  that 
it  responds  to  the  movement  of  the  mechanical  lever, 
but  if  the  magnets  are  de-energized  the  signal  blade 
goes  to  normal  and  will  not  respond  to  the  movement 
of  the  lever,  being  detached  therefrom. 

The  other  type  of  slot  is  cut  into  the  up  and  down 
rod.  When  the  magnets  are  energized  the  up  and 
down  rod  is  held  together  in  one  piece,  but  when  they 
are  de-energized  it  is  cut  in  two,  the  signal  going  to 
its  danger  position  by  gravity. 

This  slotting  of  signals  is  most  frequently  used 
on  mechanical  home  signals  at  interlocking  plants 
through  which  automatic  block  signals  are  carried, 
or  for  controlled  manual  block  signals.  The  track 
circuit  is  so  arranged  that  the  slot  magnets  are  de- 
energized  and  the  signals  go  to  normal  after  a  truck 
has  passed  them  a  few  feet.  As  long  as  a  pair  of 
wheels  is  in  the  circuit  the  slot  magnets  "refuse  to 
hold,"  as  it  is  called,  and  the  signal  cannot  be  cleared. 
After  everything  is  out  of  the  circuit,  the  lever  man 
must  restore  his  lever  to  normal,  if  he  has  not  already 
done  so,  in  order  to  "catch"  the  slot  so  that  he  may 
be  able  to  clear  the  signal  again. 

These  devices  are  very  ingenious  and  are  a  great 
safeguard  where  used,  as  the  presence  of  a  train 
in  the  section  sets  the  signal  at  stop,  while  it  requires 
the  action  of  a  human  agent  to  clear  it. 

Their  use  with  manual  block  signals  prevents  the 
possibility  of  an  operator  forgetting  to  return  his 
signal  to  normal  behind  a  train  which  he  has  admitted 
to  the  block. 


CHAPTER  XIX. 

AUTOMATIC   SIGNALS — AUTOMATIC  TRAIN    STOPS. 

The  object  to  be  attained  by  the  use  of  automatic 
block  signals,  like  that  of  manual  block  signals,  is 
simply  to  have  a  signal  displayed  in  the  stop  position 
behind  each  train  on  a  double  track  line  until  the 
train  has  gone  a  certain  distance  beyond  that  signal, 
at  which  time  a  second  signal  takes  the  place  of  the 
first  one,  and  so  on,  continuously. 

In  the  case  of  a  single  track  line  the  same  object  is 
to  be  attained  with  the  addition  that  at  all  times  a 
signal  governing  movements  in  the  direction  opposite 
to  that  in  which  the  train  is  moving  must  be  displayed 
in  the  stop  position,  some  distance  ahead  of  the  train. 

It  would  be  useless  in  a  treatise  of  the  scope  of  the 
present  to  attempt  to  give  the  reader  a  detailed  descrip- 
tion of  each  of  the  various  types  of  automatic  block 
signals  in  use,  or  of  the  many  circuit  arrangements 
by  which  their  operation  is  effected.  Volumes  could 
be  written  on  this  head  without  covering  the  entire 
field. 

The  automatic  block  signal  too  has  come  into  promi- 
nence so  recently  that  improvements  in  its  modus 
operandi  are  being  advanced  daily.  Almost  every  sig- 
nal engineer  has  some  special  method  of  applying  the 
circuits,  so  that  there  is  far  from  any  uniformity  of 
practice. 

Every  automatic  signal  arrangement  now  in  use  de- 
pends primarily  for  its  operation  upon  the  track  cir- 

294 


IN  TEEOET  AND  PEACTICE.  295 

cuit,  the  principles  of  which  have  already  been  ex- 
plained. 

The  signals  used  are  either  of  the  enclosed  disc,  or 
semaphore  type.  The  former  represents  the  first  auto- 
matic electrical  signal  to  come  into  general  use,  and 


Fig.   127.  Fig.  128.  Fig.   129. 

is  an  evolution  from  an  early  type  arranged  to  operate 
by  clock  work. 

Fig.    127   illustrates   a   common   form   of   enclosed 
disc  signal,  the  mechanism  of  which  is  very  simple, 


296  RAILWAY  SIGNALING 

consisting  of  an  electro  magnet  whose  armature  is  at- 
tached to  a  lever,  one  end  of  which  forms  a  hoop 
across  which  is  stretched  a  piece  of  fine  bunting  or 
silk. 

When  the  electro  magnet  is  energized  this  hoop 
and  its  covering  which  forms  a  disc  is  removed  from 
the  glass  covered  opening  in  the  case  and  a  white 
background  shows  through  the  glass. 

When  the  magnet  is  de-energized  this  disc  falls  by 
gravity  so  as  to  show  through  the  glass  covered  open- 
ing. 

With  home  signals,  these  discs  are  usually  made  of 
a  red  fabric  and  with  distant  signals  of  green  or 
yellow. 

The  night  indication  is  given  by  a  smaller  glass  disc 
which  moves  away  from  or  in  front  of  a  small  glass 
covered  opening  at  the  top  of  the  case,  behind  which 
an  ordinary  semaphore  lamp  is  placed. 

The  movable  parts  of  these  signals  being  enclosed 
in  the  case  which  is  made  of  dressed  and  matched 
lumber,  and  sheet  steel  is  not  exposed  to  the  weather 
and  can  be  made  very  light  and  the  movable  lever 
very  nearly  balanced.  Their  operation  is  quite  reliable 
and  they  require  very  little  repairs. 

In  spite  of  this,  however,  they  are  open  to  one  ob- 
jection, and  so  serious  a  one  at  that,  that  very  few  of 
them  are  being  installed  at  the  present  time.  This 
objection  is  that  they  are  a  color  and  not  a  position 
signal,  both  day  and  night.  The  fact  that  the  cloth 
discs  are  displayed  from  behind  a  pane  of  glass  makes 
it  impossible  to  distinguish  their  color  when  the  rays 
of  the  sun  strike  the  glass  at  certain  angles.  Wet 
driving  snow,  too,  sometimes  coats  the  glass  so  that 
the  disc  cannot  be  seen  at  all. 

Of  semaphore  signals  usable  for  automatic  block 
signals,  there  are  a  vast  number,  on  the  market,  any 
one  of  which,  if  properly  installed,  will  give  satis- 


IN  THEORY  AND  PEACTICE.  297 

factory  service.  As  a  matter  of  fact  there  is  no  more 
real  difference  between  the  various  types  than  there 
is  between  watches  manufactured  by  so  many  different 
makers. 

The  electro  gas  signal  already  alluded  to  as  having 
been  used  to  some  extent  as  a  power  distant  signal, 
is  also  applicable  to  use  as  an  automatic  block  signal. 
In  fact  this  is  true  of  any  type  of  signal  which  may 
be  used  for  a  power  distant  signal. 

Many  of  these  gas  signals  are  now  in  use,  although 
the  tendency  at  present  is  to  install  nothing  but  elec- 
tric motor  signals. 

The  Union  Switch  and  Signal  Company  manu- 
factures a  motor  signal  known  as  its  "style  B,"  in  all 
essentials  similar  to  the  signal  already  referred  to  as 
being  used  with  its  all-electric  interlocking.  As  is  the 
case  with  all  electric  signals  used  for  automatic  block- 
ing, it  is  supplied  with  a  ten-volt  motor.  The 
mechanism  of  this  signal  is  in  a  case  at  the  base  of 
the  pole  and  motion  is  transmitted  to  the  arm  plate 
by  up  and  down  rods  inside  the  pole. 

One  of  these  signals  is  illustrated  in  Fig.  128. 

The  General  Railway  Signal  Company  manufactures 
a  signal  known  as  its  "model  5,"  illustrated  in  Fig. 
129,  which  has  the  mechanism  in  a  case  at  the  top 
of  the  pole,  the  motor  being  geared  directly  to  the 
spindle,  no  up  and  down  rods  being  used. 

With  the  former  the  repairman  can  inspect,  oil  or 
repair  the  mechanism  without  climbing  the  pole ;  with 
the  latter,  he  must  climb  the  pole  to  do  so. 

The  General  Electric  Company  and  the  Hall  Signal 
Company  each  furnish  signals  with  "topmast"  and 
with  "base"  mechanism,  as  well. 

The  American  Railway  Signal  Company's,  and  the 
Federal  Railway  Signal  Company's  signals  have  base 


298  RAILWAY  SIGNALING 

mechanism.  Opinion  is  divided  as  to  which  is  the 
better  type  from  the  viewpoint  of  the  maintainer. 

There  appears  to  be  a  quite  general  impression 
amongst  railroad  officers  who  are  not  signal  en- 
gineers, that  if  a  certain  make  of  signal  is  decided 
on,  the  same  manufacturer  who  furnishes  the  signal 
must  also  furnish  all  other  parts  necessary  to  an  in- 
stallation. Such  is  far  from  being  the  case  and  fre- 
quently an  appreciable  economy  can  be  effected  by 
buying  the  signals  from  one  dealer,  the  relays  from 
another,  the  battery  shelters  from  a  third,  and  so  on. 

After  it  has  been  decided  what  type  of  signal  is  to 
be  used,  and  whether  a  normal  clear  or  normal  danger 
system  is  to  be  installed,  the  location  for  the  signals 
themselves  must  be  decided  on.  There  is  no  satis- 
factory way  of  doing  this  except  to  draw  in  the  sig- 
nals on  a  small  scale  map  of  the  line,  spaced  an  even 
distance  apart,  this  distance  or  length  of  block  being 
determined  on  beforehand.  Then  check  this  with  a 
profile  showing  the  grades,  so  as  to  prevent  as  much 
as  possible  placing  signals  in  such  situations  that  a 
train  stopped  by  one  will  be  on  an  ascending  grade 
so  steep  that  it  will  be  impossible  to  start  the  train 
again.  Curvature  also  should  be  taken  into  considera- 
tion and  signals  placed  so  that  there  will  be  as  much 
straight  track  as  possible  in  front  of  them,  in  order  to 
give  the  runner  of  an  engine  a  chance  to  see  the  posi- 
tion of  the  signal  from  some  little  distance  as  he  ap- 
proaches it.  After  the  signals  have  thus  been  sketched 
in  on  a  map,  the  signal  engineer  with  some  operating 
officer  of  the  division  on  which  the  signals  are  to  be 
placed  should  personally  visit  the  ground  and  see  if 
there  are  any  physical  reasons  why  it  would  be  in- 
advisable to  place  the  signals  as  shown.  An  exami- 
nation of  the  ground  frequently  shows  that  the  view 
of  the  signal  will  be  better  if  it  is  moved  a  few  hun- 
dred feet  one  way  or  the  other. 


IN  THEOEY  AND  PRACTICE.  299 

The  exact  position  of  switches  and  station  build- 
ings, too,  should  have  considerable  bearing  on  the 
question  of  where  to  place  automatic  block  signals. 

For  example,  if  there  is  a  facing  point  switch  in 
the  main  track  and  an  automatic  block  signal  is  to 
be  placed  anywhere  in  its  vicinity,  it  is  always  better 
to  place  it  from  1500  to  3000  feet  in  front  of  the 
switch  and  by  connecting  a  circuit  controller  to  the 
switch  points,  have  the  signal  held  at  danger  so  long 
as  the  switch  is  not  set  for  the  main  line.  Circuit  con- 
trollers (switch  boxes)  are  attached  to  every  switch 
in  automatic  territory,  so  that  if  any  of  them  facing  or 
trailing  is  open  the  signals  will  be  held  at  stop. 

At  stations  it  is  always  well  to  have  a  block  sig- 
nal in  advance  of  the  station  building,  so  that  the 
engine  runner  of  a  train  stopped  at  the  station  will 
have  the  signal  in  front  of  him.  If  the  block  in  ad- 
vance is  occupied,  and  the  signal  is  in  the  stop  posi- 
tion the  engine  runner  can  see  it,  and  will  not  start 
out  until  the  signal  goes  to  clear,  or  until  the  limit  of 
time  which  he  must  wait  before  passing  the  signal  in 
the  danger  position  has  expired.  If  the  signal  is  not 
in  view  from  the  station  he  might  start  up  and  then 
have  to  stop  again  on  reaching  it.  In  terminal  ter- 
ritory where  traffic  is  very  heavy  and  the  movements 
are  not  very  fast,  it  is  frequently  advantageous  to 
have  short  blocks — 3500  feet  to  4000  feet  long,  or 
even  shorter. 

On  some  of  our  low  grade  lines  freight  trains  con- 
taining as  many  as  eighty  cars  are  frequently  hauled. 

Most  freight  cars  now-a-days  have  bodies  thirty-six 
feet  long  and  some  forty  feet  long.  Counting  the 
engine  and  caboose,  these  trains,  therefore,  ap- 
proximate thirty-five  hundred  feet  in  length.  Where 
trains  of  this  size  are  frequently  hauled  it  does  not,  of 
course,  pay  to  make  the  blocks  any  shorter  than  thirty- 
five  hundred  feet,  as  such  trains  would  then  hold  two 


300 


RAILWAY  SIGNALING 


Fig.  130. 


IN  THEORY  AND  PRACTICE.  301 

blocks  at  a  time,  and  the  middle  signal  would  be  of 
no  advantage — merely  a  useless  expense. 

Away  from  terminals,  blocks  in  automatic  block  ter- 
ritory, are  most  often  from  one  mile  to  two  miles 
in  length.  It  is  the  common  practice  to  have  the  sig- 
nal governing  the  entrance  to  a  block  give  a  caution 
indication  if  the  second  block  is  not  clear.  That  is, 
if  there  are  two  consecutive  blocks,  A-B,  B-C,  if  the 
block  B-C  is  occupied  the  signal  at  A  would  give  a 
caution  indication;  that  is,  it  would  inform  an  engine 
runner  that  it  was  safe  for  him  to  enter  the  block 
A-B,  but  that  he  must  expect  to  find  the  block  signal 
at  B  at  stop  when  he  reaches  it.  This  practice  does 
well  enough  perhaps  where  blocks  are  not  over  a  mile 
long,  but  it  is  of  very  doubtful  advantage  where  they 
are  longer  than  a  mile.  In  the  latter  case  it  is  much 
better,  although  it  costs  more,  to  erect  a  separate  dis- 
tant signal  2500  feet  to  3000  feet  from  the  home 
block  signal. 

In  early  installations  of  automatic  block  signals,  it 

A  B  C  D 


Fig.  131. 

was  quite  often  the  practice  to  do  without  the  caution 
signal,  and  instead  use  what  is  called  an  "overlap." 

By  this  arrangement  a  train  moving  from  A  to  B 
and  from  B  to  C  would  hold  the  signal  at  A  at  danger 
behind  it  until  it  had  reached  a  point  half  a  mile  or 
so  beyond  B.  In  other  words  until  it  was  half  a  mile 
beyond  the  signal  at  B  so  as  to  have  that  much  pro- 
tection from  that  signal,  it  would  not  release  the  signal 
at  A. 

This  practice  as  it  tends  to  weaken  confidence  in  the 


302  RAILWAY  SIGNALING 

indication  given  by  the  stop  signal  is  not  to  be  recom- 
mended. 

Until  comparatively  recently  the  caution  signal, 
where  it  was  used,  was  given  by  a  caution  signal 
blade  below  the  home  signal  blade,  as  shown  in  Fig. 
130. 

The  three  position  signal  was  designed  in  order  to 
make  one  blade  give  both  the  clear  and  the  caution 
indication.  Fig.  131  illustrates  three  consecutive 
blocks  in  which  the  first  and  second,  A-B,  B-C  are 
clear,  but  the  third  one  C-D  is  occupied.  Signal  at 
A  is  at  clear,  signal  at  B  is  at  caution,  and  signal 
at  C  is  at  stop. 

Automatic  block  signals  for  single  track  railways 
are  not  in  general  favor  with  signal  engineers,  al- 
though a  great  many  of  them  have  been  installed 
during  the  past  five  years. 

A  single  track  automatic  installation  costs  about 
as  much  as  a  double  track  installation  does,  and 
adds  little  if  any  protection  except  for  following 
movements.  Trains  cannot  pass  each  other  on 
single  track  lines  except  where  passing  tracks  are 
provided.  It  is,  therefore,  useless  to  let  a  train 
pass  A  in  the  direction  of  B  after  another  train  has 
already  passed  B  moving  towards  A,  if  there  is 
no  passing  track  between  A  and  B.  One  of  the 
chief  arguments  in  favor  of  automatic  signals  is 
that  a  great  operating  expense — the  wages  paid  to 
manual  block  operators — may  be  saved  by  their 
use.  In  actual  practice  this  rarely  if  ever  works 
out.  In  the  case  of  a  single  track  railroad,  two 
trains  leave  the  initial  stations  of  a  division,  say 
one  hundred  miles  long,  at  the  same  time.  If 
there  are  no  operators  stationed  along  this  division 
the  dispatcher  starts  the  two  trains  out  with  orders 
showing  at  what  station  they  must  meet  and  pass. 
If  they  each  make  about  the  time  which  the  dis- 


IN  THEOET  AND  PRACTICE.  303 

patcher  figured  they  would  make,  they  can  keep 
this  meeting  point,  but  very  frequently  one  train 
or  the  other  meets  with  some  delay.  As  there  is  no 
means  by  which  the  dispatcher  can  reach  the  other 
train  it  arrives  at  the  meeting  point  and  waits  there, 
maybe  hours,  for  that  which  has  been  delayed,  the 
train  and  engine  men  making  overtime  and  traffic 
being  delayed.  If  on  the  other  hand  there  are 
operators  all  along  the  line  the  dispatcher  can  reach 
either  or  both  of  the  trains  and  change  the  meeting 
point  whenever  it  becomes  desirable  to  do  so.  I 
have  known  several  cases  where  automatic  signals 
were  put  in  and  operators  discharged,  who  in  a 
month  or  two  had  to  be  re-employed  in  order  to 
keep  the  business  moving  at  all  satisfactorily. 

With  all  automatic  signal  installations,  as  there 
is  a  chance  of  a  failure  of  apparatus  causing  the 
signal  to  stand  at  stop  until  repairs  have  been 
made,  it  is  customary  to  allow  engine  runners  to 
pass  the  signal  at  the  stop  position,  after  stopping 
and  waiting  a  limit  of  time  laid  down  in  the  rules 
of  the  railroad  to  whom  the  signals  belong.  For- 
merly this  time  limit  was  from  three  to  five  min- 
utes. The  tendency  now-a-days  is  to  allow  an  en- 
gine runner  to  proceed  at  once  after  coming  to  a 
full  stop,  which  usually  means  a  stop  of  a  minute, 
allowing  for  the  releasing  of  the  air  brakes.  After 
starting  up  again  the  engine  runner  is  instructed 
by  the  rule  to  proceed  cautiously,  prepared  to  stop 
within  his  range  of  vision  until  the  next  signal  is 
reached.  If  that  is  at  clear  he  may  proceed  at 
regular  speed,  but  if  that  signal  is  displayed  at 
danger  he  must  again  stop,  and  after  starting  up 
proceed  cautiously  as  before,  and  continue  so  to 
do  until  he  reaches  a  clear  signal  or  finds  an  ob- 
struction in  the  block. 

Normal    danger   automatic   block   signals   stand 


304  RAILWAY  SIGNALING 

normally  at  danger,  as  the  appellation  signifies,  and 
go  to  clear  as  a  train  approaches  them,  if  the  block 
which  they  govern  is  clear. 

Normal  clear  automatic  block  signals  stand  nor- 
mally at  clear  and  go  to  danger  after  a  train  or 
part  of  it  has  passed  them,  remaining  so  as  long 
as  the  train  remains  in  the  block  which  they  govern. 
After  the  train  has  passed  out  of  the  block  they  return 
to  the  clear  position. 

The  most  common  practice  is  to  arrange  the  sig- 
nals, either  normal  clear  or  normal  danger,  to  take 
the  danger  position  after  the  front  truck  of  the 
train  has  passed  them  from  fifty  to  one  hundred  and 
fifty  feet. 

As  before  stated,  automatic  electric  signals  are 
arranged  to  be  operated  by  a  ten  volt  motor.  When 
no  current  is  flowing  through  the  motor  the  signal 
is  at  stop.  When  a  current  is  allowed  to  pass 
through  the  motor  it  (the  motor)  revolves  and 
either  pulls  or  pushes  the  signal  blade  to  clear. 
The  current  for  the  motor  is  supplied  by  a  so-called 
"local  battery" — 16  cells — placed  near  the  signal. 
Lalande  battery  is  usually  used  for  this  purpose  as  it 
is  not  affected  by  low  temperatures. 

A  year  or  two  ago  there  was  quite  an  agitation 
amongst  signal  engineers  in  favor  of  using  storage 
batteries  for  this  purpose,  and  several  railroads 
spent  a  good  deal  of  money  providing  for  their 
use.  One  method  was  to  have  charging  plants  at 
regular  intervals  along  the  line  and  to  carry  cur- 
rent for  charging  from  them  to  the  batteries  which 
were  placed  at  or  near  the  signals.  Another  method 
was  to  have  portable  storage  batteries  which  could 
be  shipped  in  to  a  central  charging  station  where 
they  would  be  charged  and  sent  out  again  to  the 
point  where  they  were  to  be  used.  This  meant  a 
number  of  duplicate  batteries,  of  course.  From  the 


IN  THEORY  AND  PRACTICE. 


305 


fact  that  the  use  of  storage  batteries  for  this  pur- 
pose is  not  being  advocated  as  much  as  it  was  the 
inference  is  that  experiments  along  this  line  have 
not  proven  as  satisfactory  as  was  at  first  hoped. 

A   wire   leading    from   the   motor   is   attached   to 
the  hinge  of  the  track  relay  and  another  wire  is 


Fig.  132. 


attached  to  either  its  front  or  back  contact  point, 
from  there  to  one  pole  of  the  battery  and  another 
wire  is  run  from  the  other  pole  of  the  battery  to 
the  other  side  of  the  motor.  If  the  front  contact 
is  used  this  circuit  is  closed  when  the  relay  is  picked 


306 


EAILWAY  SIGNALING 


up  and  the  motor  is  energised  and  holds  the  signal 
blade  at  clear.  When  the  relay  is  down  this  cir- 
cuit is  broken,  the  motor  is  de-energised  and  the 
signal  blade  goes  to  stop  by  gravity. 

If  the  back  contact  is  used  the  reverse  is  the 
case. 

The  cases  where  the  front  or  back  contact  is 
used  will  be  explained  later. 

Fig.  132  shows  a  typical  arrangement  of  relay, 
local  battery  and  signal  motor. 

We  now  come  to  the  practical  application  of  the 
foregoing  to  a  normal  danger  signal  system. 

In  the  first  place  it  should  be  noted  that  where 
blocks  are,  say  two  miles  long  and  where  ballast 
conditions  are  such  that  short  sections  are  neces- 
sary, an  arrangement  must  be  made  by  which  the 
sections  may  be  coupled  together  so  that  several 

Y  * 


nfiond/  3/yn  repmenti'nj  o  Battery. 

•-** 


Fig.  133. 

of  them  act  as  a  unit.     Fig.  133  illustrates  how  this 
is  done. 

The  track  battery  circuit  of  the  second  section 
shown  as  section  B  is  looped  through  the  hinge 
and  front  contact  of  the  relay  of  section  A  so 
that  when  a  train  enters  section  A,  moving  in 
the  direction  of  the  arrow  „  relay  aN  drops,  breaking 
the  circuit  of  battery  b  so  that  relay  b  is  de- 
energised  and  drops  also.  As  the  same  thing  ap- 
plies to  section  C  its  relay  drops  too,  and  so  on  ad 
infinitum  for  as  many  sections  as  there  may  be 


IN  THEORY  AND  PRACTICE.  307 

in  the  block.  In  this  way  a  train  entering  a  block 
drops  all  the  relays  ahead  of  it  and  keeps  them 
down,  but  the  relay  of  each  section  picks  up  again 
as  soon  as  the  last  pair  of  wheels  passes  out  of 
that  section.  For  instance,  see  Fig.  133,  with  the 
last  pair  of  wheels  at  X,  relays  a,  b  and  c  are  down. 
With  the  last  pair  of  wheels  at  Y,  relay  a  has  picked 
up  again  but  relays  b  and  c  are  down;  with  the  last 
pair  of  wheels  at  Z,  relays  a  and  b  are  picked  up  and 
relay  c  is  down.  When  the  last  pair  of  wheels  has 
passed  out  of  section  C  all  three  relays  are  picked  up 
again. 

Now  take  Fig.  134.  The  first  section  is  what 
is  known  as  a  preliminary  or  clearing  section,  at 
the  end  of  this  is  the  signal.  Note  that  the  wire 
a  a  a  connects  the  signal  motor  with  one  pole  of 


rr* 


Fig.  134. 

the  local  battery  and  the  other  pole  of  the  local 
battery  with  the  back  contact  of  the  relay  of  the 
preliminary  section.  Another  wire  b  b  connects 
the  hinge  of  the  relay  lever  with  the  other  side  of 
the  signal  motor. 

Now  it  is  plain  that  when  the  relay  is  picked 
up  the  circuit  through  the  signal  motor  is  broken 
at  the  back  contact  of  the  relay,  but  let  a  train 
enter  the  preliminary  section  the  relay  drops,  clos- 


308 


EAILWAY  SIGNALING 


ing  this  circuit  so  that  the  current  flows  from  the 
local  battery  through  wire  a  a  a  through  the  motor 
and  back  through  wire  b  b  and  the  back  contact  of 
the  relay  to  the  battery.  This  starts  the  motor 
going  and  pulls  or  pushes  the  signal  blade  to  clear. 
As  soon  as  the  last  pair  of  wheels  has  passed  out 
of  the  preliminary  section  the  relay  picks  up  again, 
and  the  signal  goes  to  danger  because  the  current 
through  the  motor  is  broken  at  the  back  contact. 
So  far  so  good,  but  as  far  as  we  have  now  gotten 
there  is  nothing  to  prevent  the  signal  clearing  again 
if  another  train  comes  into  the  preliminary  section, 
even  if  the  first  train  has  only  gone  a  few  feet 
beyond  the  signal. 

To  insure  that  the  signal  remains  at  danger  as 


>.    b  A  M  6-  C  K. 


long  as  the  first  train  is  in  the  block  the  wire  b  b 
in  Fig.  134  is  carried  completely  through  the  block 
as  shown  in  Fig.  135,  and  is  looped  through  the 
front  contact  of  the  last  relay  in  that  block.  The 
wire  is  usually  carried  on  the  telegraph  poles  and 
is  looped  down  from  the  pole  to  the  relay  box.  In 
some  installations  it  is  looped  through  every  relay 
in  the  block  so  that  if  any  accident  should  hold 
the  last  relay  up  the  line  would  be  broken  by  one 
of  the  others,  but  the  more  general  practice  now-a- 


IN  THEOET  AND  PEACT1CE.  309 

days  is  to  loop  it  through  the  last  one  only,  this 
being  more  economical,  as  the  leads  down  from  the 
pole  line  have  to  be  rubber  covered  copper  wire, 
carried  in  trunking,  and  cost  from  $75  to  $125  each. 

Now,  therefore,  when  the  train  has  passed  the 
signal  and  into  the  block  which  that  signal  governs 
it  must,  as  before  described,  have  at  least  one  of  the 
relays  in  that  block  down,  thus  breaking  the  line 
wire  and  preventing  any  current  from  flowing 
through  the  signal  motor.  The  signal  consequently 
stays  at  danger,  even  if  another  train  comes  into 
the  preliminary  section  and  drops  its  relay. 

The  relays  are  constructed  with  as  many  as  four 
separate  levers  attached  to  the  armature,  so  that 
one  relay  will  perform  more  than  one  function. 

For  instance,  in  a  series  of  blocks  the  relay  of 
the  section  at  the  far  end  of  one  block,  breaks  the 
line  wire  for  the  signal  behind  it  with  one  of  its 
front  contacts,  and  at  the  same  time  acts  as  the 
relay  for  the  preliminary  section  of  the  signal  ahead 
with  one  of  its  back  contacts. 

This  also  is  shown  in  Fig.  135. 

It  is  sometimes  customary  to  have  the  motor 
circuit  of  the  signal  in  advance  carried  on  a  line 
wire  to  the  first  relay  in  the  block  ahead,  as  shown 
in  Fig.  137,  and  looped  through  its  back  con- 
tact so  that  the  signal  works  off  the  first  relay 
instead  of  the  last  and  begins  to  clear  as  soon  as  a 
train  enters  the  block  in  advance  if  no  train  is  to  be 
protected  by  this  signal.  This  is  a  mere  matter 
of  taste,  and  does  not  affect  the  principle  involved, 
and  is  done  on  account  of  the  distant  signals  when 
carried  on  each  pole  or  on  separate  poles  for  the  home 
signals  ahead. 

Where  distant  signals  are  used,  the  object  to 
be  gained  is  to  have  the  distant  signal  go  to  clear 
before  an  approaching  train  reaches  it  if  the  first 


310  EAILWAY  SIGNALING 

and  second  blocks  in  advance  are  clear,  and  to  stay 
at  caution  if  either  of  them  is  occupied. 

This  is  done  as  shown  in  Fig.  136  by  having 
a  line  circuit  from  the  local  battery  of  the  distant 
signal  to  the  front  contact  of  the  last  relay  in  both 
the  first  and  second  block  ahead,  and  through  the 
back  contact  of  the  relay  in  the  preliminary  section 
shown  as  P  in  the  figure. 

Now  if  there  is  a  train  in  either  block  A  or  block  B, 
relay  A  or  relay  B  is  down  and  the  distant  signal  cir- 
cuit is  broken ;  but  if  both  these  blocks  are  clear  so  that 
the  relays  are  up,  the  distant  signal  circuit  will  be 
closed  when  the  train  enters  the  preliminary  section 
P,  through  the  back  contact  of  that  relay  and  the  dis- 
tant signal  will  consequently  clear. 

The  arrangement  of  the  track  circuit  for  normal 
clear  automatic  block  signals  is  the  same  as  that 


Fig.  136. 

for  normal  danger,  except  that  there  is  no  pre- 
liminary section. 

The  relays  are  so  arranged  that  they  drop  as  the 
train  enters  the  section  they  govern,  and  stay  down 
until  the  train  is  out  of  the  block.  The  relay  of  the 
first  section  controls  the  signal. 

Distant  signals  are  sometimes  operated  by  line 
circuits,  as  shown  in  Fig.  136,  and  sometimes  by 
the  use  of  so-called  polarized  relays.  It  is  a  fact  that 
if  a  permanent  magnet  is  used  for  the  core  of  an 
electro  magnet,  it  will  fail  to  attract  its  armature  if 


RAILWAY  SIGNALING 


311 


the  current  is  sent  through  the  coil  of  the  magnet  in 
one  direction,  while  if  the  current  flows  in  the  other 
direction  the  core  becomes  a  good  magnet.  A  polarized 
relay  is  one  with  a  permanent  magnet  for  the  core. 
By  attaching  a  pole  changer  to  the  blades  of  the  home 
signal,  which  the  distant  signal  repeats,  and  also  to 
the  home  signal  blade  on  the  same  mast,  with  the 
distant  signal  blade  if  it  is  so  arranged,  the  direction 
of  the  flow  of  the  current  from  the  track  battery  may 
be  reversed  when  either  home  signal  is  at  stop  from 
what  it  is  when  they  are  at  proceed. 

By  working  the  distant  signal  off  the  front  contact 
of  a  polarized  relay  arranged  so  that  it  drops  when 
the  current  is  flowing  through  it  in  the  direction  in 
which  it  flows  when  the  home  signal  blades  are  at 
stop  the  distant  signals  will  be  at  caution  whenever 
the  home  signals  are  at  stop  whether  there  is  a  train 
between  them  or  not.  The  action  of  the  polarized  re- 


-B/ock  &- 


l^F 


.Afcr/s.- 

Here  the  arrangement  of  f&/ous  ond  Truck  Baffemna-ffir  rweneof 

'      itonHtleirJeetfooan* 
'  3/ocA  pioAt  up. 


Ob  aofpict  up  again  i 


ai-nsnqemerit 
fatth&.  '   The- 


Fig.   137. 

lay  with  a  train  in  the  section  it  governs  is  just  the 
same  as  that  of  a  neutral  relay,  (the  ordinary  relays 
are  called  neutral  relays)  as  the  current  is  practically 
cut  off  from  it  entirely  then. 

Fig.  138  illustrates  a  distant  signal  operated  through 
a  polarized  track  relay. 

This  arrangement  saves  a  great  deal  of  line  wire. 

In   the   foregoing  I   have   endeavored   to   describe 


312 


RAILWAY  SIGNALING 


clearly,  and  in  such  a  manner  that  a  person  who  has 
not  been  actually  engaged  in  the  construction  and 
operation  of  automatic  signals  and  their  dependent 
apparatus,  will  be  able  to  understand,  the  primary 
principles  on  which  these  devices  operate. 

There  are,  of  course,  many  side  issues,  such  as 
switch  indicators,  annunciators,  semi-automatic  con- 
trol of  manual  signals  at  interlocking  plants,  etc., 
which  are  outside  of  the  elementary  principles  which 
I  have  taken  as  my  text.  There  is  room  for  a  great 
amount  of  ingenuity  in  arranging  the  circuits  so  that 
one  set  of  wires  will  do  for  several  of  them  and  so 
that  one  relay  and  its  shelter  will  be  available  for 


Fig.  138. 

several  different  uses,  all  in  the  interests  of  economy, 
but  to  prolong  this  chapter  along  such  lines  would 
hardly  be  of  advantage  in  an  elementary  treatise. 

Switch  indicators  are  devices  generally  made  in  the 
form  of  a  dial  on  which  is  displayed  a  miniature  sema- 
phore. ^  These  are  put  up  at  main  line  switches.  When 
there  is  no  train  in  the  block,  the  miniature  sema- 
phore shows  clear.  When  there  is  a  train  in  the 


RAILWAY  SIGNALING  313 

block,  it  shows  danger.  Their  object  is  to  warn  train- 
men of  trains  which  may  be  in  to  clear  on  a  side 
track  not  to  open  the  switch  and  come  out  on  the 
main  track  when  a  train  is  approaching. 

Annunciators  are  devices  sometimes  taking  the  form 
of  bells  or  buzzers,  and  sometimes  discs  or  miniature 
semaphores  placed  where  a  block  operator  or  lever- 
man  can  hear  or  see  them  to  warn  him  of  the  approach 
of  trains.  They  are  generally  operated  by  a  local  bat- 
tery, circuit  from  which  is  carried  through  the  back 
contact  of  the  track  relay  of  a  section  some  distance 
away.  As  a  train  enters  this  section  the  relay  drops, 
thereby  closing  the  circuit  through  the  annunciator. 

Where  an  interlocking  plant  is  situated  in  automatic 


Fig.  139. 

block  signal  territory,  it  is  not  uncommon  to  equip 
the  signals  with  electric  slots  so  that  passing  trains 
set  them  at  danger.  This  is  called  semi-automatic 
control. 

Highway  crossing  alarm  bells  too,  may  properly  be 
considered  under  the  head  of  automatic  signals.  By 
far  the  best  practice  with  these  is  to  use  an  interlock- 
ing track  relay  placed  at  the  highway  crossing,  the 
local  circuit  for  the  bell  passing  through  its  back  con- 
tact. Fig.  139  illustrates  such  an  arrangement. 

A  train  moving  from  left  to  right  drops  the  left  side 
of  the  relay,  closing  the  bell  circuit  and  starting  the 


314  RAILWAY  SIGNALING 

bell  to  ringing.  As  the  engine  crosses  the  highway 
it  drops  the  other  side  of  the  relay,  which  on  account 
of  the  interlocking  feature  already  described  cannot 
make  its  back  contact  and  also  holds  up  the  armature 
of  the  first  side  enough  to  break  its  back  contact  as 
well,  thus  breaking  the  local  circuit  and  stopping  the 
bell's  ringing.  In  this  way  nothing  but  an  approach- 
ing train  will  ring  the  bell. 

Within  the  last  year  or  two  in  the  vicinity  of  New 
York  City,  some  automatic  signal  installations  have 
been  made  in  which  the  apparatus  was  designed  to 
operate  by  an  alternating  current  of  high  pressure, 
installations  are  as  yet  much  in  the  nature  of  experi- 
ments and  as  a  detailed  description  of  the  apparatus 
used  would  carry  us  far  into  the  study  of  electrical 
engineering,  we  will  make  no  further  mention  of  al- 
ternating current  apparatus. 

For  a  long  time  almost  all  the  line  wire  for  auto- 
matic block  signals  was  insulated,  what  is  known  to 
the  trade  as  "weather  proof"  wire  being  used.  This 
wire  is  covered  with  a  cotton  tape  dipped  in  some 
composition  to  harden  it. 

The  tendency  now  is  to  use  more  bare  wire.  Where 
it  is  well  strung  so  that  the  wires  cannot  touch  each 
other  and  form  crosses,  it  is  probable  for  all  prac- 
tical purposes  that  bare  wire  is  just  as  good  as  in- 
sulated for  power  distant  signals,  and  automatic  block 
signals  as  well.  There  is,  of  course,  some  danger 
from  crosses,  but  it  is  very  doubtful  if  after  a  year 
or  two  the  use  of  weather  proof  wire  does  a  great 
deal  to  prevent  this. 

Before  leaving  the  subject  of  automatic  signals,  a 
word  or  two  on  the  subject  of  automatic  train  stops 
may  not  be  amiss. 

There  are  no  regular  surface  steam  railroads  where 
automatic  stops  are  in  actual  use,  but  such  a  public 
clamor  for  increased  safeguards  was  raised  a  year  or 


RAILWAY  SIGNALING  315 

two  since,  because  of  several  fatal  collisions  having 
happened  in  territory  protected  by  automatic  signals, 
that  Congress  appropriated  $50,000  to  enable  the  Inter- 
state Commerce  Commission  to  investigate  this  sub- 
ject. Automatic  stops  are  in  use  on  several  elevated 
railroads  and  in  the  New  York  subway. 

The  Interstate  Commerce  Commission  appointed  a 
special  committee,  consisting  of  four  gentlemen  well 
known  to  be  interested  in  and  well  informed  on  signal 
matters.  This  committee  called  on  manufacturers  and 
inventors  to  submit  plans  of  automatic  train  stopping 
devices.  Those  who  presented  such  of  these  plans  as 
conformed  to  certain  specifications  laid  down  by  the 
committee,  were  invited  to  install  working  models  for 
several  months'  actual  service  test. 

The  tests  have  only  recently  been  closed,  and  the 
committee's  report,  if  yet  presented  to  the  Interstate 
Commerce  Commission,  has  not  been  made  public,  so 
that  it  would  not  be  fitting  here  to  express  an  opinion 
one  way  or  the  other  as  to  the  merits  of  any  particular 
device  of  this  sort,  or  of  the  practical  utility  of  the 
principle  they  embody. 

Let  it  suffice  here  to  say  that  all  such  devices  are 
intended  by  some  mechanical  means  to  apply  the  air 
brakes  to  a  train  which  has  over-run  a  stop  signal. 
On  some  elevated  railroads  they  are  used  in  lieu  of 
derails,  and  are  operated  by  levermen  through  the 
medium  of  mechanical  or  power  interlocking  levers. 

As  is  generally  known  the  air  brakes  used  on  rail- 
roads are  so  arranged  that  an  opening  made  in  the 
train  pipe  which  will  allow  the  compressed  air  con- 
tained therein  to  escape  into  the  outside  atmosphere, 
applies  the  brakes  to  the  entire  train.  By  providing 
some  sort  of  a  cock  or  valve  in  the  train  pipe,  which 
will  be  opened  on  coming  in  contact  with  a  trigger 
situated  in  the  roadbed  and  working  in  conjunction 
with  a  signal,  the  arrangement  is  complete. 


310 


RAILWAY  SIGNALING 


Fig.  140. 


-RAILWAY  SIGNALING  317 

Where  used  in  connection  with  automatic  block  sig- 
nals, a  great  many  conditions  must  be  fulfilled  by  the 
apparatus.  For  instance,  the  trigger  must  be  in  the 
position  to  apply  the  brakes  to  an  oncoming  train  so 
long  as  anything  remains  in  the  block,  or  so  long  as 
there  is  a  misplaced  switch  or  a  broken  rail  therein. 
This  necessitates  the  use  of  a  track  circuit. 

The  committee's  report  will  in  all  likelihood  be  made 
public  with  the  next  report  of  the  Interstate  Com- 
merce Commission,  and  we  will  then  be  in  a  much 
better  position  to  discuss  this  branch  of  signalling. 

Fig.  140  gives  a  list  of  conventional  signs  used  on 
plans  showing  automatic  signal  installations. 


CHAPTER    XX. 

JOINT  WORK CONTRACTS PUBLIC  AUTHORITIES ESTI- 
MATES. 

As  a  great  many  interlocking  plants  are  built  to 
protect  crossings  of  the  lines  of  two  or  more  differ- 
ent railroads,  and  as  frequently  they  are  owned 
jointly  by  the  several  companies  interested,  the 
duties  of  the  signal  engineer  require  that  he  should 
frequently  work  in  conjunction  with  signal  engin- 
eers of  other  railroads.  It  is  the  well  nigh  univer- 
sal practice  that  where  two  or  more  companies  are 
part  owners  in  an  interlocking  plant,  one  or  the 
other  of  them  maintains  and  operates  it,  and  ren- 
ders monthly  bills  against  the  other  interested 
company  or  companies  for  a  certain  proportion  of 
the  expense  of  such  maintenance  and  operation. 

The  maintenance  of  an  interlocking  plant  is  con- 
sidered as  being  that  expense  which  would  be 
necessary  to  keep  the  plant  in  good  working  order 
if  the  levermen  were  removed  and  the  plant  was 
to  be  operated  by  the  trainmen  of  each  road. 

The  operation  is  that  expense  which  would  be 
incurred  over  and  above  the  maintenance  while 
levermen  were  permanently  stationed  at  the  plant. 

Repairmen's  labor,  repair  parts,  paint,  illumin- 
ating oil  for  signals  and  lubricating  oil  are  the  prin- 
ciple items  which  go  to  make  up  the  charge  for 
maintenance. 

318 


EAILWAY  SIGNALING  319 

Levermen's  wages,  fuel,  stationery,  illuminating 
oil  for  tower  and  battery  supplies  are  those  which 
go  to  make  up  the  charge  for  operation. 

Where  a  joint  plant  is  to  be  built  a  written 
agreement  is  generally  signed  by  the  interested 
companies  which  defines  the  rights  and  obligations 
of  each  with  relation  to  the  plant,  and  specifies  the 
proportion  of  the  cost  of  maintenance  and  operation 
each  is  to  pay. 

Until  a  comparatively  recent  date  there  was  no 
uniformity  whatever  in  the  form  of  these  agree- 
ments or  contracts,  and  no  rule  by  which  either 
company's  proportion  of  the  expense  could  be 
computed.  Sometimes  a  purely  arbitrary  division 
of  the  expense  was  made;  at  other  times  the  num- 
ber of  trains  passing  through  the  interlocking  plant 
on  the  line  of  each  company  during  a  given  time 
was  used  as  a  basis,  and  again  the  number  of  levers 
In  the  service  of  each  company. 

This  latter  was  probably  the  more  equitable 
method,  but  it  led  to  a  great  deal  of  useless 
quibbling  amongst  signal  engineers,  each  trying  to 
arrange  the  interlocking  in  his  line  so  as  to  use 
as  few  levers  as  possible,  and  the  introduction  of 
power  interlocking,  wherein  a  great  many  signals 
are  selected  and  operated  by  one  lever  made  a  lever 
division  difficult  to  agree  upon. 

The  Railway  Signal  Association  has,  however, 
suggested  a  method  which  is  now  quite  generally 
accepted,  of  dividing  each  plant  into  a  number  of 
operated  units,  or  functions,  and  having  each  com- 
pany assume  that  proportion  of  the  expense  of 
maintenance  which  is  represented  by  the  ratio  of 
the  number  of  units  in  its  track  to  the  total  number 
of  units  in  the  plant. 

The  operation,  too,  is  frequently,  though  not  al- 


320  RAILWAY  SIGNALING 

ways,  divided  on  the  same  basis  as  the  mainte- 
nance. 

One  huge  advantage  of  a  division  on  the  unit 
basis  is  that  it  carries  with  it  a  redivision  at  all 
times  in  case  of  enlargements  or  additions  to  a 
plant  being  made  after  it  has  once  been  put  in 
service. 

It  is  sometimes  argued  that  the  unit  basis  is 
not  an  altogether  fair  one  because  it  quite  fre- 
quently occurs  that  some  of  the  units  in  the  track  of 
one  company  are  used  very  little,  while  all  of  those 
in  the  track  of  some  other  company  are  in  constant 
use,  and  consequently  require  more  attention  and 
repair. 

Although  this  is  no  doubt  true  to  a  certain  extent, 
it  is  almost  certain  to  be  the  case  at  some  other 
plant  operated  jointly  by  the  same  companies  that 
the  conditions  will  be  reversed,  so  that  the  matter 
works  out  to  be  as  broad  as  it  is  long,  and  the  unit 
basis  has  so  many  advantages,  is  so  elastic  and  is  so 
surely  as  equitable  as  anything  yet  suggested,  that 
those  companies  which  have  not  already  done  so 
cannot  be  urged  too  strongly  to  accept  it  at  once. 

The  table  of  operated  units  as  recommended  by 
the  Railway  Signal  Association  is  as  follows: 


Table  of  Operated  Units. 

Name  of  Operated  Unit.  Value. 

Each  signal  arm  working  in  two  or  three 
positions  1  unit 

Each  power  signal  arm  working  in  two  or 
three  positions  on  mechanical  plants,  nor- 
mal indication  locking  included 2  units 

Each  pair  of  switch  points 1  unit 


RAILWAY  SIGNALING  321 

Each  single  slip  switch  (2  pairs  of  switch 
points)  2  units 

Each  double  slip  switch  (4  pairs  of  switch 
points)  4  units 

Each  set  of  movable  point  frogs  (2  pairs  of 

frog  points) 2  units 

Each  derail 1  unit 

Each  55  feet  of  detector  bar  with  or  without 
locks  1  unit 

Each  torpedo  placer 1  unit 

Each  drawbridge  coupler 1  unit 

Each  drawbridge  rail  surface  and  alignment 
lock  for  one  pair  of  rails. 1  unit 

Each  drawbridge  leveling  and  operating  ap- 
paratus lock 1  unit 

Each  track  circuit  1  unit 

The  signal  engineer  must,  of  course,  be  fre- 
quently consulted  in  the  drawing  up  of  agreements, 
with  regard  to  interlocking  plants  at  new  crossings, 
or  at  old  crossings  where  no  interlocking  plants 
have  heretofore  existed. 

All  such  cases  may  be  roughly  classed  under  two 
general  heads : 

(1)  Cases  where  it  is  to  the  mutual  advantage  of 
each  company  to  install  the  interlocking,  and  where 
each  intends  to  assume  a  proportion  of  the  expense 
thereof. 

(2)  Cases  where  one   company,  whose   line   is 
already  built,  proposes  to  allow  another  company 
to  cross  it  at  grade,  but  in  consideration  of  the  fact 
that  it  has  prior  rights,  is  to  bear  no  proportion 
of  the  expense  of  the  interlocking,  the  junior  com- 
pany bearing  it  all. 

A  Committee  of  the  Railway  Signal  Association, 
in  the  interest  of  uniform  practice,  has  proposed 


322  RAILWAY  SIGNALING 

the  following-  as  a  form  of  contract  to  be  used  in 
cases  coming  under  the  first  head. 

THIS    AGREEMENT,  made   and   entered  into 

this day  of A.  D.  by  and  between  the 

A  and  B  Company,  hereinafter  called  the  X  Com- 
pany, party  of  the  first  part,  and  the  C  and  D 
Company,  hereinafter  called  trie  Y  Company,  party 
of  the  second  part. 

Witnesseth : 

Whereas,  the  roads  of  the  respective  parties  now 
intersect  and  cross  each  other  at ,  as  pro- 
vided for  in  an  agreement  made  and  entered  into 

the day  of A.  D.,  by  and  between  the 

E  and  F  Company,  of  the  first  part,  and  the  G 
and  H  Company,  of  the  second  part,  of  which  the 
said  X  Company  and  said  Y  Company  are  the 
respective  successors,  and, 

Whereas,  the  parties  are  mutually  desirous  of 
erecting,  renewing,  maintaining  and  operating  an 
interlocking  plant  at  said  crossing  to  facilitate  and 
render  more  safe  the  passage  of  trains  over  the  same, 
the  location  of  said  crossing  being  identified,  and 
the  said  interlocking  plant  to  be  arranged  as  shown 
upon  blueprint  dated ..,  identified  by  the  sig- 
nature of  the engineer  of  the  first  party, 

and  the engineer  of  the  second  party,  at- 
tached hereto,  marked  Exhibit  "A,"  and  hereby 
made  a  part  of  this  agreement,  and 

Whereas,  the  parties  hereto  have  agreed  upon  the 
terms  and  conditions  upon  which  said  interlocking 
plant,  as  shown  by  said  Exhibit  "A,"  shall  be  con- 
structed, renewed,  maintained  and  operated; 

Now  therefore,  in  consideration  of  the  premises, 
and  in  further  consideration  of  the  mutual  covenants 
and  agreements  hereinafter  stipulated  to  be  kept 
and  performed,  it  is  agreed  between  the  parties  for 


RAILWAY  SIGNALING  323 

the  purpose  of  defining  the  terms  and  conditions 
upon  which  said  interlocking  plant  shall  be  con- 
structed, renewed,  maintained  and  operated,  as  fol- 
lows : 

First — The  said  X  Company  agrees  to  construct 
an  interlocking  plant  as  shown  upon  said  Exhibit 
"A,"  and  in  accordance  with  the  specifications  to  be 
approved  by  the  above  named  engineers,  under  the 
operation  of  which  trains  of  either  party  may,  pur- 
suant to  the  laws  of  the  state  of ,  pass  over 

the  tracks  of  the  other  party,  without  coming  to  a 
stop.  The  cost  of  removing  any  existing  safety  de- 
vices or  appliances  shall  be  divided  in  like  manner 
as  the  cost  of  the  former  renewal  and  maintenance 
expense  of  said  devices  or  appliances  has  been  here- 
tofore divided. 

Second — The  cost  of  constructing,  renewing  and 
maintaining  said  interlocking  plant,  as  shown  upon 
said  Exhibit  "A,"  shall  be  borne  on  an  operated 
unit  basis  by  the  parties  hereto,  in  the  proportion 
that  the  total  number  of  operated  units  used  to  in- 
terlock the  tracks  of  each  of  the  respective  parties 
bears  to  the  total  number  of  operated  units  of  the 
complete  interlocking  plant,  as  shown  by  the  table 
of  operated  units  on  said  Exhibit  "A." 

Third — (a)  The  cost  of  operating  said  interlock- 
ing plant,  as  shown  by  said  Exhibit  "A,"  shall  be 
borne  equally  by  the  parties  hereto. 

(b)  The  cost  of  operating  said  interlocking  plant 
shall  be  borne  as  follows: 

Said Company  shall   pay  the  sum  of 

dollars   ($ )  per  month,  the  amount 

which  it  now  pays  for  railway  crossing  watchmen, 
their  supplies,  and  maintenance  of  railway  crossing 

Note— (a)  and  (b)  to  be  used  as  circumstances  require. 


324  RAILWAY  SIGNALING 

gates;  the  balance  of  said  operating  expenses  shall 
be  divided  equally  between  the  parties  hereto. 

Note,  (a)  and  (b)  to  be  used  as  circumstances  require; 

Fourth — All  extensions  or  changes  of  said  inter- 
locking plant  arising  from  changes  made  in  any 
existing  track  or  tracks,  or  made  to  cover  any  future 
track  or  tracks  or  connections  which  either  party 
may  have  the  right  to  construct,  or  which  may  be 
required  by  reason  of  any  changes  made  in  the 
standard  appliances  of  either  Company,  or  ordered 
by  proper  authority,  shall  be  made  by  said  X  Com- 
pany, and  the  first  cost  of  such  extensions  or 
changes  shall  be  borne  by  the  party  hereto  for 
whose  benefit  said  extensions  or  changes  are  made, 
and  the  amount  chargeable  for  renewal  and  main- 
tenance to  each  party  in  such  case  is  to  be  deter- 
mined by  the  proportion  which  the  total  number 
of  operated  units  then  used  to  interlock  the  tracks 
of  each  of  the  respective  parties,  bears  to  the  total 
number  of  operated  units  of  the  complete  inter- 
locking plant. 

Fifth- — The  renewal  and  maintenance  of  said  in- 
terlocking plant  shall  be  under  the  sole  charge  and 
control  of  said  X  Company,  and  it  shall  employ 
competent  persons  to  renew  and  maintain  the  same, 
and  such  parties  from  time  to  time  so  employed 
shall  be  considered  as  joint  employees  of  the  parties 
hereto,  and  shall  be  removed  for  good  and  sufficient 
reasons  upon  request  in  writing  of  the  general  man- 
aging officer  of  the  said  Y  Company. 

And  it  is  further  mutually  agreed  and  understood 
that  in  event  said  Y  Company  shall  in  writing  notify 
said  X  Company  of  renewals  and  repairs  that  may 
be  necessary  for  the  safe  and  proper  operation  of  the 
said  interlocking  plant,  and  if  said  X  Company 
neglects  for  a  period  of  30  days  to  make  said  neces- 
sary renewals  and  repairs,  then  said  Y  Company 
shall  have  the  right  to  make  such  renewals  and 


EAILWAY  SIGNALING  325 

repairs,  and  said  X  Company,  upon  presentation  of 
the  proper  bills  therefor,  will  pay  its  proportion  of 
the  amount  so  expended. 

Sixth — The  operation  of  said  interlocking-  plant 
shall  be  under  the  sole  charge  and  control  of  said  X 
Company,  and  it  shall  employ  competent  persons  to 
operate  the  same,  and  such  persons  from  time  to 
time  so  employed  shall  be  considered  as  joint  em- 
ployes of  the  parties  hereto,  and  shall  be  removed 
for  good  and  sufficient  reasons  upon  request  in 
writing  of  the  general  managing  officer  of  the  said 
Y  Company ;  and  it  is  further  mutually  understood 
that  either  Company  may  use  the  signalmen  in  its 
telegraph  or  telephone  service,  but  in  event  ad- 
ditional expense  is  so  incurred  on  account  of  in- 
creased wages  of  operators  over  levermen,  the  Com- 
pany using  the  operators  in  its  service  shall  bear 
the  additional  expense. 

Seventh — The  salaries  of  employes  connected 
with  maintenance,  renewal  and  operation  of  the 
interlocking  plant  shall  be  the  same  as  the  standard 
salaries  paid  by  the  X  Company  for  similar  service 
to  its  other  employes  in  the  territory  of  the  said 
X  Company's Division. 

Eighth — The  payment  of  all  bills  under  this 
agreement  shall  be  made  not  later  than  the  twenty- 
fifth  day  of  the  month  following  the  month  in  which 
said  bills  are  rendered.  The  bill  for  expense  of 
construction  shall  be  made  as  a  final  bill,  unless 
otherwise  mutually  agreed  and  understood.  In  the 
event  that  partial  bills  for  expense  of  construction 
are  rendered,  each  such  partial  bill  shall  not  only 
show  fully  the  part  of  the  construction  expense  to 
be  paid  by  such  bill,  but  shall  also  include  a  state- 
ment of  all  construction  expense  which  has  been 
covered  by  any  partial  bills  which  may  have  been 
rendered  and  paid  previously. 


326  RAILWAY  SIGNALING 

Ninth — In  making  bills  for  the  cost  and  expense 
of  constructing,  renewing  and  maintaining  said  in- 
terlocking plant,  all  labor  and  material  shall  be 
charged  for  at  actual  cost,  plus  ....  per  cent  added 
to  material  and  ....  per  cent  to  labor  for  handling 
superintendence,  use  of  tools  and  accounting. 

The  labor  for  the  operation  of  said  plant  shall 
be  charged  for  at  its  actual  cost,  without  the  ad- 
dition of  any  percentage. 

Tenth — Each  of  the  parties  hereto  will,  without 
cost  to  the  other,  furnish  and  install  its  own  de- 
rails, switch  rods,  special  switch  and  derail  timbers, 
insulated  track  joints,  crossarms,  pins  and  insul- 
ators, and  will  renew  and  maintain  them  from  time 
to  time  thereafter;  likewise,  without  cost  to  the 
other  party,  do  all  the  track  work  and  grading  along 
its  own  tracks  necessary  to  prepare  the  same  for  the 
installation  of  said  interlocking  plant,  and  will  also 
provide  and  maintain  proper  drainage  upon  its  right 
of  way. 

Eleventh — Each  of  the  parties  hereto  will,  at 
its  own  expense,  keep  all  switches  and  derails  in  its 
own  tracks  free  from  ice,  snow,  dirt  or  other  ob- 
structions which  may  interfere  in  any  way  with 
the  proper  working  of  said  interlocking  plant,  and 
in  case  either  party  fails  so  to  do,  the  other  party 
shall  have  the  right  to  enter  upon  the  premises  of 
the  party  at  fault  and  remove  such  ice,  snow, 
dirt  or  other  obstructions,  in  which  event  the  party 
at  fault  shall  reimburse  the  party  doing  such  work 
for  all  expense  thereby  incurred,  plus  ....  per  cent 
to  cover  superintendence,  use  of  tools  and  account- 
ing- 
Twelfth— Each  party  hereto  shall  pay  for  all  loss, 
damage  and  expense  caused  by  its  separate  agents 
or  employes,  either  to  the  interlocking  plant,  to 


RAILWAY  SIGNALING  327 

the  property  of  the  other  party  or  to  others  not 
parties  to  this  agreement. 

All  loss,  damage  and  expense  caused  by  the  in- 
dividual negligence  of  employes  connected  with  the 
construction,  renewal,  maintenance  or  operation  of 
the  interlocking  plant,  or  by  the  combined  negli- 
gence of  such  parties  hereto,  or  by  failure  of  any 
part  of  the  interlocking  plant,  shall  be  borne  and 
paid  for  by  the  party  hereto  that  may  be  using  the 
interlocking  plant  at  the  time  such  loss,  damage 
and  expense  occurs,  and,  if  same  shall  occur  while 
the  trains  of  both  of  the  parties  hereto  are  at  the 
crossing,  or  shall  be  caused  by  the  combined  negli- 
gence of  the  separate  employes  of  the  parties 
hereto,  each  party  therein  involved  shall  bear  and 
pay  for  all  loss,  damage  and  expense  caused  to  its 
own  property,  or  to  persons  or  property  in  its 
charge;  all  other  loss,  damage  and  expense  caused 
as  above  shall  be  borne  and  paid  for  equally  by  the 
parties  therein  involved. 

Thirteenth — It  is  further  distinctly  understood 
and  agreed  that  any  and  all  agreements  relative  to 
said  crossing  existing  between  the  parties  hereto,  or 
their  predecessors,  so  far  as  they  conflict,  or  are 
inconsistent  with  the  terms  and  provisions  of  this 
agreement,  are  hereby  annulled,  but  in  all  other 
respects  shall  continue  in  force  and  virtue. 

Fourteenth — Should  any  dispute  arise  between 
the  parties  to  this  agreement  concerning  obliga- 
tions or  rights  of  either  of  them  hereunder,  the  same 
shall  be  referred  to  a  board  of  three  arbitrators,  one 
to  be  chosen  by  each  party  hereto  and  the  third 
by  the  two  so  chosen.  If  either  party  shall  fail 
to  appoint  its  arbitrator  within  fifteen  (15)  days 
after  the  party  desiring  arbitration  has  appointed 
its  arbitrator,  and  given  written  notice  to  the  other 


328  EAILWAY  SIGNALING 

of  such  appointment  and  of  the  matter  proposed  to 
be  arbitrated,  then  the  arbitrator  so  appointed  shall 
appoint  an  arbitrator  for  the  defaulting  party,  and 
the  two  so  appointed  shall  appoint  the  third  to  com- 
plete the  board  as  above  provided,  and  said  board  so 
appointed  shall  hear  and  decide  the  dispute  and 
assess  the  expenses  of  arbitration.  The  decision 
of  said  arbitrators  chosen  in  either  of  said  ways, 
or  that  of  a  majority  of  them,  shall  be  final  and 
conclusive  between  the  parties  upon  the  matters 
concerning-  which  arbitration  was  demanded. 

Fifteenth — The  provisions  of  this  agreement  shall 
be  binding  upon  and  inure  to  the  benefit  of  the  par- 
ties hereto,  their  successors,  lessees  and  assigns. 

In  testimony  whereof  the  parties  have  caused 
these  presents  to  be  executed  in  duplicate  by  their 
respective  proper  officers  as  of  the  day  and  year 
first  above  written. 

The  A.  &  B.  R.  R.  Co. 
Attest :  By 


Secretary. 
Seal. 

The  C.  &  D.  R.  R.  Co., 
Attest:  By. 


Secretary. 
Seal. 

The  same  Committee  is  understood  to  be  en- 
gaged upon  a  similar  form  to  cover  cases  coming 
under  the  second  head,  but  as  its  recommendation 
has  not  yet  been  made  public,  I  shall  offer  the  fol- 
lowing, which  my  experience  has  shown  to  be  a 
very  serviceable  form. 


RAILWAY  SIGNALING  329 

THIS    INDENTURE,    made   this day  of 

A.  D ,  by  and  between  the  A.  B.  & 

C.  Railway  Company,  hereinafter  styled  the  C. 
Company,  and  the  E.  F.  &  G.  Railway  Company, 
hereinafter  styled  the  G.  Company. 

Witnesseth. 

That  the  C.  Company,  in  consideration  of  the 
sum  of  One  Dollar  to  it  paid  by  the  G.  Company, 
the  receipt  whereof  is  hereby  acknowledged,  and 
in  further  consideration  of  the  faithful  performance 
by  the  G.  Company  of  all  its  agreements  herein 
contained,  hath  granted  and  by  these  presents  doth 
grant  unto  said  G.  Company  upon  the  several  con- 
ditions hereinafter  set  forth,  the  right  to  lay  down, 
maintain  and  operate  a  single  track  railway  of 
standard  gauge  over  and  across  the  right  of  way 

and  existing  main  track  of  the Division  of 

the  railway  of  the  C.  Company,  chiefly  in  the 

half  of  the quarter  of  section 

in  Township of  Range , 

in County, ,  so  that  the  center 

lines  of  the  tracks  of  the  respective  parties  hereto 
shall  intersect  at  the  point  designated  by  "A"  upon 
the  identified  plat  hereto  attached  and  made  part 

hereof,    and    at    the    angle    of degrees    and 

minutes  upon  said  plat  represented. 

Subject  always  to  the  observance  and  perform- 
ance by  the  G.  Company  of  all  and  singular  the 
following  conditions,  covenants  and  agreements  to 
be  by  it  observed,  kept  and  performed,  to-wit ; 

First.  It  is  a  condition  of  the  aforesaid  grant, 
and  the  G.  Company  agrees,  that  notwithstanding 
said  grant,  the  C.  Company  shall  have  the  right  to 
retain  the  tracks  now  owned  and  operated  by  it  at 


330  BAILWAY  SIGNALING 

the  place  of  crossing  aforesaid,  and  may  at  any 
and  all  times  hereafter  there  lay  down,  maintain 
and  operate  such  other  and  further  tracks  as  it 
may  deem  necessary,  and  that  the  G.  Company  shall 
not  and  will  not  at  any  time  or  in  any  manner  im- 
pair the  usefulness  of  any  of  the  aforesaid  tracks, 
whether  now  or  hereafter  constructed. 

Second.  It  is  a  further  condition  of  the  aforesaid 
grant  that  the  G.  Company  shall,  and  said  Com- 
pany also  covenants  and  agrees  that  it  will,  when- 
ever thereto  notified  by  the  Chief  Engineer  of  the  C. 
company,  furnish  and  put  in  place  at  its  own  ex- 
pense, and  in  strict  conformity  to  the  plans,  specifi- 
cations and  directions  of  said  Chief  Engineer,  all 
such  crossing  frogs,  movable  points,  crossing  signals, 
gates,  targets  and  other  appliances,  as  said  Chief 
Engineer  shall  at  any  time  require  for  making  and 
protecting  all  crossings,  present  or  future,  of  the 
C.  Company's  tracks  now  or  hereafter  constructed 
at  or  near  the  point  aforesaid ;  and  that  it  shall  and 
will  at  its  own  expense  in  like  manner  forever 
maintain,  repair  and  renew  all  such  frogs,  signals, 
gates,  targets  and  other  appliances,  and  shall  and 
will  pay  all  the  wages  of  such  flagmen  as  the  C. 
Company  may  be  required  by  law  or  ordinance,  or 
as  its  managing  officer  may  deem  necessary,  to 
employ  in  operating  said  signals  and  gates,  and  the 
cost  of  all  supplies  required  in  such  operation. 

Third.  It  is  a  further  condition  of  the  aforesaid 
grant  that  the  G.  Company  shall,  and  said  Company 
also  covenants  and  agrees  that  it  will,  at  its  own 
expense,  forever  maintain  and  keep  in  good  repair, 
the  substructure,  roadbed,  and  ties  at  the  crossing 
aforesaid,  and  will  keep  all  the  frogs,  guard  rails 
and  switches  thereat,  and  at  the  junction  of  the  con- 
necting and  transfer  tracks  hereinafter  mentioned 
with  the  tracks  of  the  C.  Company,  securely  blocked 


RAILWAY  SIGNALING  331 

and  protected,  so  as  to  make  them  as  free  as  pos- 
sible from  danger  to  the  employes  of  the  C.  Com- 
pany ;  and  if  the  G.  Company  shall  neglect  or  fail  to 
perform  promptly  and  strictly  any  of  its  covenants 
contained  in  this  or  in  the  next  preceding  section 
hereof,  then  and  in  every  case  the  C.  Company  may 
construct,  repair  or  renew,  as  the  case  may  require, 
any  of  the  crossings  or  appurtenances  in  said  sec- 
tions mentioned,  and  the  G.  Company  shall  and 
will  promptly  repay  to  the  C.  Company  the  entire 
cost  of  all  the  material  furnished  and  work  done 
by  it  in  such  construction,  repair  or  renewal. 

Fourth.  It  is  a  further  condition  of  the  afore- 
said grant  that  the  C.  Company  shall  be  entitled 
to,  and  will,  furnish  and  erect  at  or  suitably  near 
to  the  place  of  crossing  aforesaid,  but  wholly  at  the 
expense  of  the  G.  Company,  and  in  accordance  with 
plans,  specifications  and  requirements  of  the  Chief 
Engineer  of  the  C.  Company,  an  interlocking  and 
derailing  plant,  with  all  such  machinery,  apparatus 
and  appurtenances  (all  hereinafter  briefly  designated 
as  "interlocking  plant")  as  said  Engineer  may  re- 
quire for  the  operation  thereof,  and  will  connect  the 
same  with  the  tracks  of  the  respective  parties  hereto ; 
that  it  will,  at  like  expense  of  the  G.  Company,  at  all 
times  maintain  such  interlocking  plant  in  proper 
condition  and  repair;  and  shall  be  entitled,  at  the 
like  expense  of  the  G.  Company,  to  connect  the  same 
with  any  additional  track  or  tracks  which  it,  the 
C.  Company,  may  lay  across  said  track  of  the  G. 
Company  at  or  near  said  place  of  crossing;  that 
it  will  at  like  expense  of  the  G.  Company,  furnish 
the  signalmen  and  all  supplies  necessary  for  the 
operation  of  such  interlocking  plant;  and  that  the 
G.  Company  shall,  and  it  hereby  agrees  that  it  will, 
repay  to  the  C.  Company  all  the  cost  of  such  inter- 
locking plant,  and  of  the  installation  and  original 


332  RAILWAY  SIGNALING 

connection  thereof,  all  the  cost  of  any  such  ad- 
ditional connections,  and  all  the  monthly  expenses 
of  the  maintenance,  repair  and  operation  of  said 
interlocking  plant,  upon  presentation,  from  time  to 
time,  of  proper  monthly  bills  of  such  cost  and  ex- 
penses respectively;  the  C  Company  shall  and  will 
upon  complaint  of  the  G.  Company,  for  reasonable 
cause  stated,  remove  any  agent  or  servant  from 
service  in  or  about  such  interlocking  plant. 

Fifth.  It  is  a  further  condition  of  the  aforesaid 
grant,  and  the  G.  Company  also  agrees,  that  so  long 
as  the  C.  Company  shall  maintain  fences  up  to  the 
point  of  intersection  of  the  G.  Company's  tracks  with 
the  respective  boundary  lines  of  the  C.  Company's 
premises,  the  G.  Company  shall  and  will  maintain, 
in  good  order,  proper  cattle  guards  at  the  points 
of  intersection  aforesaid,  to  prevent  animals  from 
straying  upon  the  C.  Company's  premises  from  the 
track  or  grounds  of  the  G.  Company. 

Sixth.  And  the  G.  Company  further  agrees  that 
it  will  at  all  times  when  so  required  by  the  Chief 
Engineer  of  the  C.  Company,  make  the  crossing 
frogs  at  the  crossing  aforesaid  conform  to  such 
changes  as  the  C.  Company  may  make  in  the  section 
of  its  rails  laid  on  the  approaches  thereto ;  and  that 
if  a  device  be  manufactured  for  the  purpose  of  giving 
a  continuous  rail  over  a  crossing  on  the  line  having 
the  right  of  way  over  the  same,  it,  the  G.  Company 
will  at  its  own  expense,  when  thereto  requested, 
put  in  such  device  at  the  above  mentioned  crossing 
and  connect  the  same  with  the  interlocking  plant 
aforesaid. 

Seventh.  It  is  a  further  condition  of  the  afore- 
said grant,  and  the  G.  Company  also  agrees,  that 
in  the  passage  of  trains  over  the  aforesaid  crossing, 
if  passenger  trains  of  each  party  hereto  arrive 
thereat  simultaneously,  the  trains  of  the  C.  Com- 


RAILWAY  SIGNALING  333 

pany  shall  have  precedence  over  the  trains  of  the 
G.  Company ;  and,  in  like  case,  the  freight  trains  of 
the  C.  Company  shall  have  precedence  over  the 
freight  trains  of  the  G.  Company ;  but  in  every  case 
a  passenger  train  shall  have  preference  over  a 
freight  train. 

Eighth.  It  is  a  further  condition  of  the  afore- 
said grant  that  the  G.  Company  shall,  and  said 
Company  covenants  and  agrees  that  it  will,  pay  all 
the  cost  of  any  connecting  or  transfer  track  which 
may  be  at  any  time  required  at  the  place  of  crossing 
aforesaid,  whether  such  track  be  ordered  by  com- 
petent authority  or  put  in  by  agreement  between  the 
parties  hereto. 

Ninth.  It  is  a  further  condition  of  the  aforesaid 
grant  that  the  G.  Company  shall,  and  said  Company 
also  covenants  and  agrees  that,  anything  herein 
contained  to  the  contrary  notwithstanding,  it  will 
at  all  times,  and  it  does  hereby,  indemnify  the  C. 
Company  against  all  loss,  cost,  damage  or  expense 
of  any  kind  which  said  last  named  Company  may 
suffer,  or  for  wrhich  it  may  become  liable,  in  con- 
sequence of  any  neglect  or  failure  of  said  G.  Com- 
pany strictly  to  keep  and  perform  all  its  covenants 
and  agreements  in  this  contract  contained.  And 
said  G.  Company  further  agrees  that  it  will  at  all 
times,  and  it  does  hereby,  assume  all  risks,  loss  or 
damage  to  its  own  property,  or  to  property 
and  persons  in  its  employ  or  care,  or  resulting  from 
the  death  of  any  such  person,  which  shall  in  any 
wise  arise  from  the  operation  of  said  interlocking 
plant  by  employes  of  the  C.  Company,  and  will 
save  said  Company  harmless  from  all  such  loss,  risk 
or  damage  and  from  all  consequent  expense. 

Lastly.  The  grants,  covenants  and  stipulations 
hereof  shall  extend  to  and  be  binding  upon  the 
respective  successors  and  assigns  of  the  parties 


334  EAILWAY  SIGNALING 

hereto;  provided,  however,  that  all  rights  and  priv- 
ileges hereinabove  granted  shall  cease  and  become 
void  unless  the  same  shall  be  exercised  by  the  G. 
Company  within  on  year  from  the  date  hereof. 

IN  WITNESS  WHEREOF,  the  C.  Company 
and  the  G.  Company  have  caused  these  presents  to 
be  signed  by  their  proper  officers,  and  their  cor- 
porate seals  to  be  hereto  affixed  and  attested,  the 
day  and  year  first  above  written. 

A.  B.  &  C.  Ry.  Co., 
Attest:  By 


E.  F.  &  G.  Ry.  Co., 
Attest :  By  ... 


Although  the  form  of  contract  proposed  by  the 
committee  of  the  Railway  Signal  Association  does 
not  include  it,  I  have  always  found  it  very  con^ 
venient  to  insert  a  clause  in  a  joint  expense  contract 
whereby  each  party  agrees  to  paint  its  own  signal 
blades  and  masts  from  time  to  time  as  they  shall 
require  painting,  free  of  cost  to  the  other  party  or 
parties. 

Each  company  generally  has  its  own  standards 
with  which  the  other  companies  are  not  always 
familiar,  and  as  almost  every  Railroad  Company 
sends  out  painters'  gangs  to  paint  its  station  build- 
ings, water  tanks,  switch  target  and  so  forth,  each 
year,  it  is  no  real  hardship  to  take  charge  of  its 
own  signals. 

Some  signal  engineers  are  very  arbitrary  in  their 
demands  to  have  their  own  specifications  followed 
to  the  most  minute  details,  even  where  some  other 
company  maintains  a  plant  in  which  they  are  in- 


RAILWAY  SIGNALING  335 

terested.  Where  the  maintaining  company  is  a 
responsible  one,  and  no  company  which  is  not  re- 
sponsible should  be  allowed  to  take  charge  of  the 
maintenance,  it  is  always  much  better  to  allow  that 
company  to  use  its  own  standard  material  through- 
out the  plant,  except,  of  course,  in  the  case  of  sig- 
nals where  each  company  should  insist  on  having 
its  own  standard  colors  and  aspects. 

The  laws  of  many  States  require  that  where  there 
is  a  grade  crossing,  a  junction  or  a  drawbridge 
trains  must  come  to  a  full  stop  before  moving  over 
such  dangerous  point,  unless  proper  interlocking  is 
provided.  Where  such  laws  exist,  the  Railroad  Com- 
missions are  given  authority  to  lay  down  rules  for 
the  construction  of  interlocking  plants,  and  to  have 
inspections  made  thereof.  No  railroad  being  al- 
lowed to  run  its  trains  over  such  places  at  speed 
until  a  proper  permit  is  granted  by  the  Railroad 
Commission  to  do  so. 

Sometimes  the  Railroad  Commissioners  them- 
selves see  to  the  inspection  of  new  plants,  but  it  is 
quite  frequently  the  case  that  the  Commission  em- 
ploys a  Consulting  Engineer  to  pass  upon  technical 
matters  of  this  sort.  This  latter  plan  cannot  be 
too  highly  commended  as  advantageous  to  the  rail- 
roads and  to  the  public  as  well.  In  most  cases  the 
rules  require  that  a  full  set  of  plans  consisting  of  a 
copy  of  the  track  plan  showing  the  signals,  switches, 
derails,  etc.,  a  copy  of  the  dog  sheet  and  a  copy 
of  the  locking  sheet  shall  be  filed  with  the  Com- 
mission for  approval  before  the  work  is  started. 
When  the  work  is  completed,  on  proper  notification 
from  the  railroad  company,  an  inspecting  officer 
visits  the  plant  and  if  he  finds  it  satisfactory  issues 
a  permit. 

The  duty  of  providing  the  necessary  plans,  meet- 
ing the  inspecting  officer  and  making  any  required 


336  RAILWAY  SIGNALING  i 

revision  or  alteration  in  plans  or  plant,  usually  falls 
upon  the  signal  engineer. 

For  these  reasons  every  signal  engineer  should 
make  it  his  business  to  thoroughly  familiarize  him- 
self with  the  laws  and  regulations  of  each  State 
through  which  his  railroad  passes,  so  far  as  these 
matters  go. 

It  may  be  called  to  the  reader's  attention  here 
that  it  is  a  very  good  plan  to  show  the  profile  of 
each  of  the  lines  for  a  couple  of  miles  either  side 
of  the  crossing  or  junction,  and  on  either  side  of 
the  bridge,  if  a  draw  bridge,  on  the  track  plan. 
Some  Commissions  require  this  and  some  do  not, 
but  it  is  a  good  plan  to  show  it  anyway. 

Of  course  the  signal  engineer  is  frequently  called 
on  to  furnish  estimates  of  the  cost  of  contemplated 
work.  It  would  be  difficult  in  a  treatise  of  this  nature 
to  lay  down  any  hard  and  fast  figures  on  the  cost  of 
signal  work,  as  the  prices  of  material  vary  from  time 
to  time  and  the  scale  of  wages  paid  is  not  uniform  in 
all  sections  of  the  country. 

Nevertheless  I  shall  endeavor  to  give  a  few  rough 
figures  which  may  help  a  beginner. 

Plain  mechanical  interlocking,  without  any  accesso- 
ries may  be  roughly  estimated  at  $275  per  working 
lever,  exclusive  of  the  cost  of  the  tower.  The  cost  of 
towers  for  a  sixteen-lever  machine,  which  is  the  mini- 
mum size  that  should  be  built,  varies  from  $750  to 
$1,800,  according  to  the  method  of  construction  em- 
ployed by  the  railroad  whose  tower  it  is,  and  it  would 
be  useless,  therefore,  to  give  any  figures  here  on  cost 
of  towers.  For  each  power  distant  signal  at  a  mechani- 
cal interlocking  plant  add  $275;  for  each  mechanical 
time  lock  add  $100;  for  each  electric  locking  circuit 
add  $200,  and  for  each  indicator  or  annunciator  add 
$100.  These  figures  are  approximations  only,  but  they 


RAILWAY  SIGNALING  337 

will  make  an  estimate  within  15  per  cent  of  the  actual 
cost  in  most  cases. 

If  a  closer  estimate,  than  the  above  figures  would 
give,  is  desired,  there  is  nothing  to  be  done  but  to 
make  out  a  complete  bill  of  material  from  the  track 
plan.  The  signal  companies'  catalogues  give  list  prices 
for  all  material  which  these  companies  furnish,  and  the 
discounts  given,  if  any,  are  known  to  all  purchasing 
agents,  so  that  a  very  accurate  estimate  on  the  cost  of 
material  may  be  made. 

As  for  the  labor,  an  estimate  on  that  is  largely  a 
matter  of  experience  and  the  local  scale  of  wages. 

With  the  scale  of  wages  paid  throughout  the  Mis- 
sissippi and  Missouri  valleys  plain  mechanical  inter- 
locking should  be  put  in  for  $50  per  lever  labor.  This 
does  not  include  the  tower,  and  it  means  that  the  signal 
men  will  not  be  delayed  waiting  for  material  or  track 
work,  which  always  adds  to  the  cost. 

This  will  also  cover  power  distant  signals  and  time 
locks.  For  electric  locking  circuits,  indicators  or  an- 
nunciators, add  $50  each. 

As  an  aid  by  which  any  reader  who  may  wish  to 
draw  up  a  bill  of  material  for  a  mechanical  interlock- 
ing plant  may  check  himself  the  following  items  ap- 
pear on  a  complete  bill  of  material  for  one  recently 
built  to  protect  a  crossing  having  power  distant  sig- 
nals on  one  line,  and  mechanical  distant  signals  on  the 
other,  and  several  side  track  switches.  All  catalogue 
references  are  omitted. 

INTERLOCKING  MACHINE,  improved  Saxby  and  Farmer, 
or  Style  A.  Give  number  of  working  levers,  number 
of  spare  spaces.  State  how  many  levers  are  for  pipe 
and  how  many  for  wire  connection,  and  if  any  levers 
are  to  be  equipped  with  electric  locks  for  back  locks 
or  route  locking,  so  state,  or  if  time  locks  are  re- 
quired, so  state.  Enclose  locking  sheet  or  copy  of 


338  RAILWAY  SIGNALING  i 

track  plan  from  which  locking  sheet  may  be  made 
with  order. 

VERTICAL  CRANKS,  VERTICAL  DEFLECTING  BARS  OR  ROCK- 
ING SHAFTS,  for  leadout. 

HORIZONTAL  DEFLECTING  BARS  OR  BOX  CRANKS,  for 
leadout. 

HORIZONTAL  CRANKS. 

COMPENSATORS. 

PIPE  CARRIERS,  giving  number  required  of  each  differ- 
ent "way." 

TRANSVERSE  PIPE  CARRIERS,  i,  2  and  3  way. 

SOLID  JAWS,  tanged  for  1-inch  pipe. 

SCREW  JAWS,  tanged  for  1-inch  pipe. 

PIPE  LUGS. 

POINT  ADJUSTING  SCREWS. 

LAYOUTS  FOR  SWITCHES.  These  include  detector  bars, 
tie  plates,  front  and  lock  rods,  bolt  locks,  rail  clips, 
special  switch  adjustments,  facing  point  locks  or 
switch  and  lock  movements,  etc.,  and  are  listed 
assembled  in  the  signal  companies'  catalogues,  so 
that  a  great  deal  of  itemization  may  be  saved  by 
ordering  them  in  this  way. 

Signal  companies   require  that   in   ordering,  the 
following  information  be  given : 

Type  of  facing  point  lock   or    switch    and    lock 
movement  desired. 

Type  of  front  and  lock  rod. 
Type  of  tie  plate. 

Type  of  bolt  lock  (number  of  way  and  whether 
pipe  or  wire  connected). 

Type  of  detector  bar  and  rail  clip,  giving  size  and 
pattern  of  rail  on  which  same  are  to  be  used. 

LAYOUTS  FOR  DERAILS,  giving  same  information  as 
above. 

WIRE  CARRIERS. 


RAILWAY  SIGNALING  33d 

VERTICAL  CHAIN  WHEELS,  for  inside  of  tower. 

BOX  CHAIN  WHEELS,  for  leadout. 

HORIZONTAL  CHAIN  WHEELS. 

MECHANICAL  DISTANT  SIGNALS. 

POWER  DISTANT  SIGNALS. 

HOME  SIGNALS. 

DWARF  SIGNALS. 

RELAY  BOXES,  for  the  distant  signals  (if  catalogue  ref- 
erence for  signal  does  not  show  them). 

RELAYS,  for  power  distant  signals,  250  to  500  ohm  re- 
sistance. 

RELAYS,  for  track  circuit,  4  ohm.  resistance. 

BATTERY  CHUTES. 

RELAYS  INTERLOCKING  (4  OHM),  if  required  for  elec- 
tric locking. 

ELECTRIC  LOCKS,  if  same  have  not  been  ordered  with 
the  machine. 

WIRE  EYES. 

SPLIT  LINKS. 

WlRE  ADJUSTING  SCREWS. 

The   foregoing  covers   material  manufactured  by 
the  Signal  Companies  and  is  to  be  ordered  from  them. 
What  follows  may  as  well  be  made  in  the  railroad 
company's  shops  or  bought  of  local  dealers. 
ROUNDELS,  red,  yellow,  green,  for  arm  plates. 
ROUNDELS,  blue  or  purple,  for  back  lights. 
ONE-FOURTH  INCH  STRAIGHT  LINK  CHAIN  for  chain 

wheels. 

ONE-INCH  SIGNAL  PIPE  PLUGGED  AND  RIVETTED. 
SEMAPHORE  LAMPS. 

CAST  IRON  PIERS  FOR  CRANKS  AND  COMPENSATORS. 

SHORT  BOLTS  FOR  SAME  (two  to  each). 


340  ,  RAILWAY  SIGNALING 

CONCRETE  PIPE  CARRIER  FOUNDATIONS. 

HOOK  BOLTS  FOR  SAME  (two  to  each) . 

TOPS  FOR  FOUNDATIONS,  either  metal  or  3-inch  x  8-inch 
oak. 

Give  length,  if  oak. 

LUMBER,  one-inch  common  pine  for  concrete  forms. 

CEMENT  AND  OTHER  CONCRETE  MATERIAL. 

WASHERS. 

IRON,  24-INCH  x  2>£-iNCH,  for  tie  straps  around 
switches. 

LAG  SCREWS,  24-iNCH  x  5-iNCH,  to  fasten  down  tie 
straps. 

HOOK  BOLTS,  ONE-INCH  DIAMETER,  to  fasten  high  sig- 
nal poles  to  foundations. 

HOOK  BOLTS,  THREE-QUARTER-INCH  DIAMETER,  to  fast- 

en  dwarf  signals  to  foundations. 

HOOK     BOLTS,     ONE-HALF-INCH     DIAMETER,     to     fasten 

dwarf  signal  chain  wheels  to  foundations. 

MACHINE  BOLTS,  THREE-QUARTER-INCH  DIAMETER, 
various  lengths  required. 

DERAILS. 

OAK  TIMBERS,  for  use  as  special  ties  at  switches  and 
derails. 

RAIL  BRACES,  to  fit  on  tie  plates. 

PAINT,  for  pipe  lines. 

PAINT,  for  poles. 

PAINT — red,  green,  yellow — for  levers  and  blades. 

OIL,  LARD  OR  VASELINE,  for  lubricating  locking  of  ma- 
chine. 

OIL,  LINSEED,  for  thinning  paint. 

OIL,  BLACK,  for  oiling  up  before  plant  goes  in  service 
and  for  drilling. 

BLACKSMITHS'  COAL. 


RAILWAY  SIGNALING  341 

LINE  WIRE,  for  power  distant  signals. 

CROSS  ARMS,  for  carrying  line  wire  on  poles. 

CROSS  ARM  BRACES,  for  carrying  line  wire  on  poles. 

INSULATORS,  for  carrying  line  wire  on  poles. 

CROSS  ARM  PINS,  for  carrying  line  wire  on  poles. 

THROUGH  BOLTS,  for  attaching  cross  arms  to  poles. 

BATTERY  CELLS,  Lalande. 

BATTERY  SHELTERS,  to  hold  local  battery  at  distant  sig- 
nals, unless  furnished  with  the  signal. 

TRUNKING,  1-inch  x  1-inch  groove,  with  capping. 

TRUCKING,  i^-inch  x  i^-inch  groove,  with  capping. 

OAK  STAKES,  3-inch  x  4-inch  x  4  feet,  for  trunking 
and  wire  lines  to  distant  signals. 

WIRE,  No.  12,  rubber  covered  copper,  for  connections 
to  pole  line  and  inside  wiring. 

TAPE,  adhesive,  for  wrapping  joints. 

TAPE,  outside,  for  covering  joints. 

SOLDER. 

SOLDERING  FLUX. 

NAILS,  for  nailing  trunking  to  stakes. 

NAILS,  for  nailing  capping  to  trunking. 

NAILS,  for  nailing  concrete  forms  together. 

BATTERY  CUPBOARD,  for  battery  in  tower. 

LIGHTNING  ARRESTERS. 

PORCELAIN  CLEATS,  for  inside  wiring. 

GROUND  RODS,  for  lightning  arrester  grounds. 

WIRE,  No.  9  galvanized  steel  semaphore,  for  wire  con- 
nected signals. 
If  an  estimate  on  the  cost  of  a  power  interlocking 

plant  is  desired,  $400  per  operated  unit  will  give  it 

approximately,    exclusive    of    the    tower    and    power 

house,  if  a  separate  one  is  to  be  built. 

As    there    is    no    complete    price    list    for    power 


342  SAILWAY  SIGNALING 

apparatus,  if  a  closer  estimate  is  needed  it  is  best  to 
ask  one  of  the  signal  companies  to  make  a  bid  on  the 
plant. 

Where  the  railroad  company  is  to  install  a  power 
plant  with  its  own  men,  the  wire  trunking,  storage 
battery  generator,  trunking,  stakes,  and  in  fact  every- 
thing not  listed  on  the  signal  companies'  catalogues, 
may  sometimes  be  bought  advantageously  of  other 
dealers.  The  cost  of  labor  installing  a  power  plant  is 
anywhere  from  $50  to  $75  per  operated  unit. 

The  signal  companies  will  bid  on  material  only, 
or  material  and  installation,  as  requested. 

The  cost  of  automatic  block  signals  varies  with  the 
number  of  signals  used  and  the  number  of  switches 
to  be  insulated.  Some  carefully  prepared  figures  got- 
ten out  recently  are  as  follows.  The  reader  may  take 
them  for  what  they  are  worth : 

Unbroken  track  circuit,  per  mile $257.35 

Each  switch  in  circuit,  additional 151.08 

Each  three-position  signal  in  place,  including 

lamp  roundels,  relay,  foundation,  connections 

to  pole  line,  battery  and  battery  shelter 475-28 

Each  one  blade  two-position  signal  in  place,  as 

above  421.75 

Each  two  blade  two-position  signal  in  place,  as 

above  495.06 

Line  wire  in  place — 

Bare  copper  wire,  per  mile 45.00 

Weather-proof  copper,  per  mile 70.00 

There  are  usually  from  three  to  nine  wires  in  each 
circuit. 

These  figures  do  not  cover  handling  material  and 
any  extra  track  work  which  may  be  necessary  in  pre~ 
pairing  tracks  for  the  track  circuit,  so  in  using  them 
for  estimating  purposes  it  is  best  to  add  10  per  cent 
to  cover  contingencies. 


CHAPTER  XXI. 

CONCLUSION. 

The  problem  of  railway  signaling  is  a  complex  one, 
and  not  easily  solved.  As  a  problem,  too,  it  has  but 
recently  come  to  the  fore,  so  that  a  great  deal  of  the 
work  already  done  has  been  along  experimental  lines, 
resulting,  as  is  always  the  case  at  such  times,  in  much 
labor  being  thrown  away. 

The  use  of  signals  forms  a  language — a  sign  lan- 
guage it  is  true,  but  just  as  much  a  language  as 
though  it  was  written  and  spoken.  This  language 
is  for  the  use  and  guidance  of  eminently  practical 
men,  men  so  thoroughly  trained  along  certain  lines 
of  thought  and  action  that,  as  the  saying  goes,  a 
wink  to  them  is  as  good  as  a  nod.  These  men  are  so 
placed  that  they  not  only  have  a  number  of  other 
responsible  duties  to  perform  besides  interpreting  sig- 
nals, but  are  often  in  situations  where  the  meaning  of 
a  signal  must  be  grasped  instantly.  It  is,  therefore, 
greatly  to  be  desired  that  the  signals  should  speak  in 
as  few  words  as  possible,  and  that  those  words  should 
carry  an  unequivocal  meaning,  as  in  the  case  of 
military  or  naval  manoeuvers,  where  an  officer's  com- 
mands are  simply  "do  this"  or  "do  that,"  and  no 
breath  is  wasted  on  superfluous  explanations. 

The  watch  officer  on  the  bridge  of  a  steamship,  on 
finding  himself  approaching  dangerously  near  another 
vessel,  does  not  say  to  the  helmsman,  "To  avoid  run- 
ning into  that  ship  ahead  put  your  helm  a-port."  He 

343 


344:  RAILWAY  SIGNALING 

simply  says  "port  your  helm"  and  leaves  it  to  the 
helmsman  to  find  out  later  why  the  order  was  given. 

Like  every  other  science  which  has  been  developed 
of  late  years  since  academicians  became  so  thick  in 
the  land,  railway  signaling  has  been  subjected  to  con- 
siderable scientific  criticism.  Some  of  the  academi- 
cians, too,  have  even  found  their  way  into  the  signal 
departments  of  our  railroads,  and  an  attempt  has  been 
honestly  made  by  them  to  develop  a  coherent  and 
cohesive  table  of  signal  aspects  which  would  show 
no  inconsistencies  under  the  critical  inspection  of  the 
college  professor.  At  the  present  such  attempts  ap- 
pear to  have  rather  over-reached  themselves  and  there 
is  a  marked  reactionary  tendency,  aiming  at  sim- 
plicity, even  if  a  few  inconsistencies  have  to  be  swal- 
lowed. 

The  English  language  itself  is  rife  with  inconsist- 
encies. The  Frenchman  or  the  German,  on  taking  it 
up,  asks  the  question,  How  can  I  learn  a  language 
where  p-1-o-u-g-h  spells  plow,  t-h-r-o-u-g-h  spells 
throo,  t-o-u-g-h  spells  tuff,  etc. 

Esperanto  is  doubtless  a  language  of  much  more 
correct  construction  than  English,  but  does  anyone 
really  think  that  we  are  going  to  abandon  English 
and  substitute  Esperanto  for  practical,  every  day  use 
in  this  great,  big,  busy  world  of  ours.  Even  the 
recent  attempt  of  a  President  of  the  United  States, 
backed  up  by  the  weight  of  the  United  States  Gov- 
ernment, to  simplify  our  spelling  has  apparently  made 
no  impression  on  the  practical  mind  of  the  every  day 
man. 

So  it  is  with  signaling.  Never  mind  how  thor- 
oughly our  academic  friend  of  the  signal  profession 
develops  a  language  of  fixed  signals,  the  practical  man 
whose  hand  is  on  the  throttle  lever  of  an  engine  will 
group  the  aspects  into  three  classes — those  which 
mean  proceed  without  limitation,  those  which  mean 


EAILWAY  SIGNALING  345 

proceed  cautiously,  and  those  which  mean  stop.  It 
does  not  make  any  difference  to  him  whether  a  signal 
is  a  "stop  and  stay"  or  a  "stop  and  proceed"  signal 
until  after  he  has  stopped.  There  is  time  enough 
then  for  him  to  begin  to  differentiate..  It  is  quite 
possible  to  give  a  vast  number  of  signs  by  the  use  of 
the  semaphore.  Chappe,  who  first  developed  it  for 
visual  telegraphy,  gave  one  hundred  and  sixty-three 
different  signals  with  it,  but  what  good  is  it  going  to 
do  to  elaborate  so  when  the  man  for  whose  use  the 
signals  are  placed  only  needs  three,  or,  at  most,  four, 
indications  ? 

The  use  of  signals  on  a  railway  is  for  one  pur- 
pose, and  one  only,  viz.,  to  enable  a  great  number  of 
trains  to  move  swiftly  with  safety.  If  trains  moved 
as  they  once  did  on  the  Stockton  and  Darlington 
Railway,  at  three  or  four  miles  an  hour,  we  could  get 
along  very  well  without  fixed  signals,  but  if  we  are 
going  to  run  trains  at  forty-five,  fifty  or  sixty  miles 
an  hour,  experience  has  taught  us  that  we  cannot  do 
so  with  safety  unless  we  provide  signal  protection. 
The  signal  which  will  help  us  to  accomplish  this  is 
what  is  needed.  As  far  as  I  am  aware  we  are  not 
having  railway  accidents  because  the  signal  aspects 
we  have  used  for  years  are  not  good  enough,  but 
because  we  do  not  have  enough  signals,  such  as 
they  are. 

In  the  foregoing  pages  I  have  endeavored  to  lay 
before  the  reader  the  general  theory  of  American 
railway  signal  practice,  with  as  much  descriptive  detail 
of  the  machinery  used  therein,  and  of  the  earlier  prac- 
tice from  which  that  of  today  has  grown,  as  my  space 
permitted  of. 

That  there  is  no  branch  of  railroad  engineering 
which  is  receiving  more  attention  at  the  present  time, 
cannot  be  doubted.  That  a  properly  developed  signal 
system,  thoroughly  installed  on  a  railroad,  adds  won- 


346  RAILWAY  SIGNALING 

derfully  to  the  safety,  as  well  as  the  facility  of  train 
movement,  is  now  an  established  fact,  and  yet,  as 
regards  American  railroads,  signal  engineering  is 
still  in  its  infancy. 

The  introduction  of  electricity  into  the  field  of  sig- 
naling, although  it  opened  up  a  vast  range  of  new 
possibilities,  has  also  to  some  extent  had  a  deterrent 
effect  on  the  progress  of  general  signaling  on  Amer- 
ican railroads.  This  statement  may  appear  extraor- 
dinary to  some  readers,  but  I  think  I  can  show  that 
I  am  right. 

The  cost  of  even  the  simplest  mechanical  signal 
arrangement,  when  carried  out  systematically  over  an 
entire  railroad  system,  is  enormous,  and  the  introduc- 
tion of  electrical  accessories  has  added  vastly  to  the 
cost,  without,  in  my  opinion,  adding  proportionately 
to  the  safety  secured  by  the  signals. 

To  illustrate:  A  plain,  single  track  railroad  cross- 
ing protected  by  a  mechanical  interlocking  plant, 
without  any  accessories  whatever,  affords  a  certain 
proportion  of  protection.  That  is,  there  is  less  likeli- 
hood of  damage  to  property  or  injury  to  persons  oc- 
curring at  that  crossing  than  if  there  was  no  inter- 
locking. We  add  a  mechanical  time  lock,  which  pre- 
vents the  leverman  from  opening  a  derail  in  the  face 
of  an  approaching  train,  making  him,  like  the  girl  in 
Dickens'  story — count  "five  and  twenty"  before  he 
acts.  This  adds  approximately  four  per  cent  to  the 
cost  of  the  plant,  and  in  all  probability  adds  that 
much  more  safety. 

If,  however,  we  add  electric  route  locking,  we  in- 
crease the  cost  about  25  per  cent,  and  add  very  little, 
if  any  more  safety  in  practice,  although  theoretically 
no  doubt  we  do. 

This  means  that  if  for  a  given  sum  of  money  we 
can  protect  one  hundred  and  twenty-five  crossings 
with  simple  mechanical  interlocking  and  time  locks, 


IN  THEORY  AND  PRACTICE.  347 

we  can  only  protect  one  hundred  and  four  if  we  use 
electric  locking. 

As  most  railroads,  like  other  businesses,  can  devote 
only  so  much  money  to  this  sort  of  improvement,  the 
extension  of  the  field  of  signaling  is  being  retarded 
by  the  extra  cost  of  the  electrical  accessory. 

Hasty  and  ill-advised  legislation,  too,  has  often 
defeated  the  very  purpose  for  which  it  was  intended, 
by  compelling  railroads  to  comply  with  certain  im- 
practical requirements  if  they  installed  signals,  which 
would  make  the  cost  virtually  prohibitive. 

I  wish  to  say  here,  distinctly,  that  this  statement  is 
not  to  be  taken  as  applying  to  all  legislation.  Many 
states  have  very  wise  and  just  laws  regarding  the 
protection  of  grade  crossings,  junctions  and  draw- 
bridges, and  where  such  exist  no  one  recognizes  the 
benefit  to  be  derived  therefrom  more  readily  than  the 
signal  engineer. 

A  case,  however,  which  does  apply,  is  that  of  the 
recently  enacted,  so-called,  "nine  hour  law,"  by  which 
Congress  forbids  any  railroad  doing  an  interstate  busi- 
ness from  keeping  a  block  operator  on  duty  more 
than  nine  hours  out  of  twenty-four.  This  means  that 
where  a  manual  block  station  is  to  be  kept  open 
twenty-four  hours  a  day  three  men  must  be  employed 
there  instead  of  two,  as  was  the  former  practice.  This 
is  a  direct  increase  of  fifty  per  cent  in  the  cost  of 
operation  and  has  probably  done  more  to  retard  the 
advance  of  manual  block  signaling  than  any  one  thing 
that  could  have  been  done. 

The  work  of  the  ordinary  block  operator  is  cer- 
tainly not  heavy. 

He  has  a  great  deal  of  spare  time  on  his  hands 
while  on  duty  which  he  may  devote  to  reading  and 
other  mental  relaxation.  Any  one.  who  has  ever 
worked  at  night  around  a  railway  station  has  some 
idea  of  the  number  of  games  of  chess  and  checkers 


348  RAILWAY  SIGNALING 

going  on  over  the  wires  during  the  wee  small  hours 
of  the  morning. 

Had  the  law  been  drawn  to  read  about  as  follows, 
viz.:  that  no  railroad  should  keep  a  block  operator 
on  duty  more  than  twelve  hours  out  of  twenty-four 
and  not  more  than  seventy-two  hours  during  any  one 
week,  it  would  have  accomplished  all  that  the  present 
law  can  possibly  accomplish  and  would  have  appealed 
to  the  sense  of  justice  of  every  railroad  officer.  This 
would  mean  that  each  operator  would  get  one  day  a 
week  off.  The  railroads  would  have  had  to  employ 
an  extra  man  for  each  six  regular  men,  whose  duty 
it  would  have  been  to  travel  from  station  to  station, 
relieving,  or,  as  the  expression  is,  "spelling"  each 
regular  man  as  his  turn  came  around. 

I  have  recently,  since  commencing  to  write  this 
chapter,  read  a  little  book  by  Mr.  Raynar  Wilson,  Eng- 
lish signal  engineer  and  author,  entitled  "The  Safety 
of  British  Railways."  No  American  can  read  what 
Mr.  Wilson  says  without  being  forcibly  impressed  by 
two  points  which  stand  out  par  excellence  beyond  all 
the  rest  of  the  work. 

1.  That  for  thirty-five  years  there  has  been  a  steady 
decrease  in  the  accidents  per  train  mile  on  the  rail- 
roads of  Great  Britain,  until  a  point  has  been  reached 
where  a  person  traveling  by  rail  may  be  said  to  be 
safer  than  he  is  sitting  at  home  in  his  own  house. 

2.  That  this  wonderful  condition  has  been  devel- 
oped by  the  railroad  managements,  voluntarily,  and 
unhampered  by  acts  of  Parliament — two  general  laws 
bearing  on  the  use  of  safety  appliances  having  been 
enacted  during  thirty-five  years.    Both  these  laws  are 
far-reaching,  and  well-drawn,  so  that  they  have  re- 
quired no  amendments. 

There  is  no  reason  to  believe  that  the  managements 
of  American  railroads  like  to  pay  out  claims  for  loss 
and  damage  to  freight  and  for  personal  injuries  any 


IN  THEOEY  AND  PEACTICE.  349 

more  than  their  cousins  over  the  water,  and  were  it 
not  for  the  uncertainty  which  is  always  present  as  to 
what  Congress  and  the  various  State  Legislatures 
will  do  next,  there  is  little  doubt  that  signaling  in  this 
country  would  be  much  further  advanced  than  it  is. 

Another  retarding  element,  and  one  for  which  the 
railroads  themselves  are  largely  responsible,  is  the 
lack  of  uniformity  of  practice.  The  American  Rail- 
way Signal  Association,  although  it  has  done  much 
good  work  during  its  short  life,  has  not  yet  succeeded 
in  establishing  uniformity  in  either  signal  aspects, 
indications  or  colors.  The  three  position  signal  is  as 
violently  opposed  by  some  as  it  is  supported  by  others, 
and  the  same  may  be  said  of  the  upper  and  lower 
right  hand  quadrant,  while  a  sect  has  recently  ap- 
peared strongly  advocating  an  upper  left  hand 
quadrant  signal.  In  fact,  our  national  spirit  of  rest- 
lessness and  wishing  a  change  appears  as  strongly  in 
our  signal  practice  as  in  other  ways.  There  is  no 
doubt  that  so  long  as  the  members  of  this  Association 
cannot  agree  amongst  themselves  as  to  what  is  the 
best  practice,  a  great  many  signal  engineers  are  diffi- 
dent about  recommending  further  installations  at  the 
present  time. 

Being,  I  suppose,  by  nature,  conservative  in  all 
things,  I  am  free  to  confess  that  I  fail  to  see  the 
necessity  for  any  change  in  what  has  been  heretofore 
the  most  general  of  any  practice  in  this  country,  viz. : 
the  lower  right  hand  quadrant  sixty  degree  signal. 
I  believe  that  the  painting  of  all  blades,  both  home 
and  distant,  yellow,  or  some  other  conspicuous  color, 
would  be  an  advantage,  and  the  general  adoption  of  a 
green  light  for  the  clear  indication  at  night  would  also 
be  a  good  thing.  These  changes  can  be  made  at  a 
trifling  expense  in  any  existing  installation.  The 
ninety  degree  signal,  either  upper  or  lower  quadrant, 
I  consider  a  positive  step  backwards.  Even  where  the 


350  RAILWAY  SIGNALING 

arm  plate  is  of  such  shape  as  to  carry  the  blade  some 
little  distance  away  from  the  mast,  the  blade  and 
mast  parallel  to  each  other  do  not  make  as  conspicuous 
a  signal  by  any  means  as  where  they  form  an  angle 
with  each  other. 

The  three  position  signal  was  first  installed  and 
has  had  its  fairest  tryout  on  a  railroad  whose  signal 
officers  are  today  foremost  in  advocating  a  signal  sys- 
tem in  which  each  semaphore  must  display  two  lights 
at  night.  This  would  indicate  that  their  experience 
with  the  one  lamp  mast  of  the  three  position  system 
had  not  proven  entirely  satisfactory. 

By  far  too  few  American  signal  engineers  have 
had  actual  experience  in  the  operating  department  of 
a  railroad,  and  consequently  many  of  them  fail  to 
grasp  the  real  utility  of  signals.  For  the  same  reason, 
much  thought,  time  and  money  has  been  spent,  I 
cannot  but  believe  useless — in  attempts  to  make  our 
signal  devices  fool  proof,  by  doing  away  with  the 
"human  equation." 

As  a  distinguished  signal  engineer  has  tersely  put 
it,  "In  this  country  we  spend  millions  in  an  endeavor 
to  make  our  apparatus  fool  proof,  while  in  England 
they  spend  hundreds  to  eliminate  the  fool,  and  appear 
to  get  better  results." 

There  is  no  doubt  that  American  railroad  manage- 
ments could  advantageously  give  more  attention  to 
educating  their  train  and  engine  men  as  well  as  their 
block  operators  in  a  better  understanding  of  the  mean- 
ing and  advantage  of  fixed  signals  of  all  sorts.  If 
the  same  attention  was  given  to  this  subject  as  is  being 
given  to  instruction  in  the  use  of  air  brakes,  much 
good,  I  am  certain,  would  result. 

As  regards  the  use  of  automatic  block  signals.  My 
observation,  and  I  have  watched  them  for  many  years, 
both  from  an  operating  and  from  an  engineering  point 
of  view,  does  not  lead  me  to  believe  that  they  are  the 


IN  THEOEY  AND  PRACTICE.  351 

panacea  for  all  the  ills  on  a  railroad,  which  for  a 
long  time  they  were  given  the  credit  of  being.  Sta- 
tistics, carefully  compiled  by  a  special  committee  of 
the  Interstate  Commerce  Commission,  showed  that  for 
the  period  covered  more  collisions  occurred  per  train 
mile  in  automatic  block  territory  than  in  manual  block 
territory.  There  is  more  than  one  reason  by  which 
such  a  condition  may  be  explained.  With  manual 
block  signals,  engine  runners  know  that  when  a  signal 
is  set  at  stop,  it  is  because  the  block  operator  in  charge 
of  it  set  it  so,  and  that,  in  case  they  disregard  the 
signal,  the  operator  in  self-defense  will  report  it. 
Again,  manual  block  signals  are,  as  a  rule,  placed  at 
much  less  frequent  intervals  than  automatic  signals, 
and  are  always  at  a  station  interlocking  tower,  or 
block  cabin,  the  location  of  which  is  well  fixed  in  the 
runner's  mind.  A  manual  block  signal,  too,  is  a  "stop 
and  stay"  signal,  which  means  that  when  displayed 
at  stop,  an  engine  runner  is  forbidden  to  pass  it  until 
it  is  cleared,  or  he  is  given  written  authority  to  do  so. 
With  automatic  signals,  on  the  other  hand,  there  is 
no  one  permanently  stationed  in  their  vicinity  whose 
duty  it  is  to  report  an  engine  runner  who  fails  to 
stop  for  one ;  they  stand  out  in  isolated  places  without 
any  distinguishing  landmark  near,  so  that  a  man  who 
is  looking  after  an  injector  or  gauge  cock  may  slip 
by  one  without  noticing  it,  and  the  rules  of  every 
railroad  allow  the  runner,  after  he  has  stopped  for  an 
automatic  signal,  to  proceed  immediately  without 
waiting  for  it  to  go  to  clear.  The  temptation  to  a 
man  with  a  poorly  steaming  engine  and  a  heavy 
train,  knowing  this  rule,  to  fail  to  come  to  the  stop, 
is  at  times  well  nigh  irresistible.  I  have  more  than 
once  subjected  myself  to  ridicule  by  making  the  state- 
ment that  I  considered  the  automatic  block  signal  as 
representing  a  transition,  and  that  I  did  not  consider 
that  it  was  here  to  stay,  but  would  eventually  be  sup- 


352  RAILWAY  SIGNALING 

planted  by  a  manual  block  system.  Nevertheless,  I 
shall  here  repeat  that  statement,  and  let  it  go  down 
into  history  as  my  honest  opinion.  By  this  I  do  not 
wish  to  be  understood  as  meaning  that  the  automatic 
signal  will  ever  entirely  vanish.  Around  large  ter- 
minals, where  very  short  blocks  are  necessary  on  a 
six  or  eight  track  line,  the  automatic  signal  may  be 
used  to  advantage.  In  such  cases  a  large  enough 
maintenance  force  to  keep  the  signals  in  good  working 
order  at  all  times  can  be  kept  on  hand,  but  from 
long  stretches  of  line  through  the  country,  I  believe 
they  will  some  day  disappear. 

A  great  many  American  railroads,  especially  in  the 
West,  have  very  heavy  traffic,  all  in  one  direction  at 
certain  hours  of  the  day.  For  instance,  it  is  every 
railroad's  endeavor  to  arrange  its  schedules  so  as  to 
bring  its  passenger  trains  into  large  terminals  such 
as  Chicago,  St.  Louis,  St.  Paul,  Kansas  City  and 
Omaha,  early  in  the  morning.  At  the  same  time,  all 
of  the  points  named  being  live  stock  centers,  stock 
trains  are  being  hurried  in  for  the  early  markets,  as 
well  as  packing  house  products;  and  merchandise,  for 
city  delivery,  is  wanted  at  receiving  freight  houses 
as  early  as  possible. 

In  the  evening,  on  the  other  hand,  this  condition  is 
reversed.  Passenger  trains  are  arranged  to  leave 
during  the  late  afternoon  and  early  evening,  so  that 
merchants  who  have  come  in  on  the  morning  trains 
may,  after  having  a  day  for  business  in  the  city,  return 
to  their  homes  by  the  next  morning.  Empty  stock 
cars  are  being  rushed  back  to  the  loading  points  and 
the  city  merchandise  loaded  during  the  day  is  started 
out  as  soon  as  the  freight  houses  close,  so  as  to  get 
as  far  as  possible  on  its  journey  by  next  morning. 

With  double  track  railroads  leading  into  such 
places,  therefore,  as  long  as  the  regular  direction  of 
traffic  is  rigidly  adhered  to,  one  track  is  virtually  idle 


IN  THEORY  AND  PRACTICE.  353 

for  many  hours  at  a  time  while  the  other  may  be 
congested  to  the  point  of  causing  serious  and  even 
expensive  delays. 

With  railroads  as  much  as  any  other  business,  it  is 
true  economy  to  keep  all  of  the  plant  earning  money 
all  of  the  time,  and  the  practice  of  reversing  the 
direction  of  traffic  on  one  track  at  such  congested 
times  is  fast  becoming  popular. 

An  automatic  block  system  does  not  lend  itself 
readily  to  such  an  arrangement,  while  a  well  or- 
ganized manual  block  system  does,  although  the  move- 
ments against  the  current  are  controlled  by  train 
orders  instead  of  by  signals.  By  having  no  crossovers 
between  the  two  tracks,  except  at  block  stations,  trains 
may  be  given  dispatchers'  orders  and  crossed  over  at 
any  point  by  the  block  operator,  especially  if  the  cross- 
over switches  are  interlocked.  The  block  operator 
being  responsible  for  the  proper  manipulation  of  the 
switches,  and  also  being  advised  of  all  train  move- 
ments for  a  block  on  either  side  of  him,  is  in  the  best 
position  possible  to  detect  a  mistake  in  an  order  if 
one  should  be  made.  As  orders  given  to  engine  and 
train  men  at  such  times  are  for  immediate  action, 
they  are  not  subject  to  the  objections  raised  against  a 
dispatching  system,  where  orders  are  given  on  which 
the  recipient  is  not  expected  to  act,  possibly  for  an 
hour  or  maybe  a  longer  time  than  that  during  which 
he  may  forget  that  he  received  the  order.  Where  ad- 
vantage is  systematically  made  of  the  idle  time  of  one 
track  in  this  way,  I  have  never  yet  heard  of  an  acci- 
dent's occurring  through  such  an  arrangement. 

As  long  as  there  was  no  accepted  method  of  com- 
munication between  stations  except  by  telegraph,  the 
introduction  of  manual  block  systems  was  seriously 
retarded  by  the  scarcity  of  telegraph  operators.  Pro- 
fessional telegraph  operators  who  would  accept  posi- 
tions as  block  operators  at  the  wages  which  railroads 


354  EAILWAY  SIGNALING  \ 

could  afford  to  pay  for  such  service  were,  as  a  rule, 
beginners — young  men  who  expected,  as  soon  as  they 
became  proficient  enough,  to  be  able  to  secure  better 
pay  in  other  positions.  The  introduction  of  the  tele- 
phone for  block  purposes  has  made  it  possible  for 
railroads  to  use  a  different  and  more  permanent  class 
of  men  for  this  work,  which  is  bound  to  result  in 
more  efficient  service  in  the  future. 

The  danger  point  on  a  railroad  is  within  station 
limits.  It  is  there  that  irregular  movements  are  made. 
That  is,  switching  is  done  there  and  trains,  engines 
or  cars  are  crossed  over  from  one  track  to  another. 
Almost  all  switches  connecting  with  main  tracks  are 
there.  There  is  probably  no  one  thing  by  which  a 
railroad  can  secure  more  additional  safety  for  its 
money  than  by  interlocking  all  main  track  switches 
and  putting  their  proper  manipulation  in  the  hands 
of  one  man.  By  careful  consideration  of  the  operating 
conditions,  most  of  the  important  main  track  switches 
at  a  station  can  be  brought  within  the  limits  of  a 
mechanical  interlocking  plant.  The  exception  to  this 
is  the  far  out  switches  at  the  ends  of  passing  tracks. 
Unless  power  interlocking  is  used,  the  cost  of  which 
is  generally  prohibitive,  these  cannot  be  operated  from 
the  station.  It  is  well,  therefore,  to  provide  distant 
signals  which  may  be  bolt  locked  with  or  connected  to 
these  switches  with  facing  point  locks,  as  described  in 
an  earlier  chapter.  At  stations  so  situated  that  the 
view  of  the  station  limits  from  the  main  line  is  ob- 
scured, a  home  and  distant  signal  placed  outside  of 
the  station  limits,  to  be  set  at  stop  and  caution  by 
trainmen  employed  on  trains  using  the  main  track 
at  the  station,  will  be  found  an  additional  and  val- 
uable safeguard.  Automatic  signals  are  sometimes 
used  for  this  purpose,  or  if  it  is  not  advisable  to  install 
a  track  circuit,  and  the  distance  that  these  signals 
must  be  placed  from  the  levers  which  operate  them  is 


IN  THEORY  AND  PRACTICE.  355 

so  great  that  the  signals  cannot  be  operated  with  cer- 
tainty by  mechanical  means,  electric  signals  operated 
in  the  same  manner  as  power  distant  signals  are  oper- 
ated, may  be  used. 

The  duties  of  a  signal  engineer  are  such  that  it 
is  a  much  mooted  question  whether  he  belongs  in  the 
engineering  or  operating  department  of  a  railroad. 
This  is  a  matter  that  railroads  generally  differ  about. 
Whether  he  reports  to  an  operating  or  an  engineering 
head,  it  is  the  universal  custom  to  have  him  take 
charge  of  any  signal  construction  work  which  may  be 
contemplated.  He  should,  therefore,  be  in  close 
enough  touch  with  the  construction  department  to  be 
able  to  give  advice  as  to  the  most  advantageous  layouts 
for  switches  and  sidetracks  at  points  where  inter- 
locking plants  and  block  signals  are  to  be  installed. 

My  own  experience  has  been  that  it  is  much  cheaper 
and  more  satisfactory  in  every  way  for  a  railroad 
company  to  employ  its  own  signal  construction  force 
and  install  its  interlocking  and  signal  work  itself, 
buying  the  material  on  the  open  market  to  suit  its 
own  standards. 

Some  large  companies  prefer,  however,  to  contract 
for  all  their  new  work. 

I  have  not  said  anything  in  regard  to  the  construc- 
tion of  towers  because  this  is  a  matter  which  on  most 
large  railroads  is  handled  by  the  architect  or  super- 
intendent of  buildings  and  not  by  the  signal  engi- 
neer. There  is  really  very  little  that  can  be  said  from 
the  signal  engineer's  point  of  view.  Almost  any  form 
of  construction  should  satisfy  him,  provided  he  is 
given  a  solid  support  for  the  machine,  ample  window 
space  and  a  building  of  solid  enough  construction  to 
insure  its  keeping  warm  during  cold  weather.  In  my 
opinion  many  railroads  build  their  towers  in  a  much 
more  expensive  and  elaborate  manner  than  is  neces- 
sary. Where  a  brick  or  concrete  building  is  to  be 


356  EAILWAY  SIGNALING  i 

used,  it  should  be  made  amply  large  enough  to  allow 
for  later  enlargements  to  the  machine.  My  rule  is 
to  build  no  such  tower  for  less  than  a  forty  lever 
machine,  even  though  a  much  smaller  machine  is  to 
be  used  for  the  time  being.  Frame  towers  may  be 
enlarged  very  cheaply  so  that  it  hardly  pays  to  build 
them  larger  than  necessary  for  present  requirements. 
The  use  of  hot  water  heaters  in  interlocking  towers 
is  becoming  quite  popular.  It  can  be  recommended  as 
economical  and  cleanly. 

Where  a  power  interlocking  machine  is  used  and 
the  storage  battery  is  to  be  placed  in  the  basement  of 
the  tower,  the  rack  or  case  for  the  battery  cells  should 
be  arranged  so  that  light  may  be  had  on  the  jars 
from  each  side.  This  enables  the  maintainers  to  see 
through  the  electrolyte  and  watch  the  performance 
of  the  plates. 

Towers  should  never  be  placed  closer  than  eight 
feet  from  the  nearest  rail  to  the  face  of  the  tower. 
If  there  is  a  likelihood  of  another  track's  being  built 
on  the  tower  side  of  an  existing  track,  the  tower 
should  be  placed  a  minimum  distance  of  23  feet  from 
the  center  of  the  latter. 

Lamps  with  very  large  hoods  or  shades,  which  may 
be  suspended  from  the  ceiling,  are  to  be  had.  These 
give  a  good  light  in  the  operating  room  but  do  not 
throw  the  light  out  through  the  windows.  Their  use 
will  be  found  very  satisfactory.  The  manipulation 
chart,  and  all  notices  which  it  is  necessary  to  post  in 
the  operating  room,  should  be  neatly  framed  and  the 
levermen  should  be  compelled  to  keep  the  tower  tidy. 
The  locking  beds  of  Saxby  and  Farmer  machines 
should  be  covered  with  a  canvas  or  wooden  cover  to 
protect  them  from  sand  and  dirt  which  would  cut 
the  locking  dogs  and  crosslocks. 

Since  the  American  Railway  Signal  Association 
issued  its  standard  specifications  for  mechanical  inter- 


IN  THEOEY  AND  PRACTICE.  357 

locking  material,  the  parts  manufactured  by  any  of 
the  companies  are  interchangeable.  This  Association 
has  also  sent  out  a  standard  specification  for  contract- 
ors to  work  to,  so  that  uniform  work  may  be  had 
from  any  of  the  companies  doing  business  in  this  line. 
These  specifications,  for  both  mechanical  and  power 
interlocking  will  be  found  in  the  appendix. 


THE  END. 


SPECIFICATIONS  FOE  MECHANICAL  INTEELOCKING. 
General. 

1.  Specifications.  6. 

2.  Drawings.  7. 

3.  Supervision.  8. 

4.  Alterations.  9. 

5.  Permits. 
Detail. 

10.  Intent.  15. 

11.  Supplementary  Data.  16. 

12.  Material  and  Workman-     17. 

ship.  18. 

13.  Transportation.  19. 

14.  Track  Work. 
Interlocking  Stations. 

20.  Building. 
Interlocking  Plant. 

21.  Machine.  39. 

22.  Leadout.  40. 

23.  Pipe  Lines.  41. 

24.  Pipe   Carriers.  42. 

25.  Compensation.  43. 

26.  Horizontal  Cranks.  44. 

27.  Vertical  Cranks.  45. 

28.  Switch  and  Lock  Move-     46. 

ment.  47. 

29.  Deflecting  Bars.  48. 

30.  Jaws  and  Lugs.  49. 

31.  Offsets.  50. 

32.  Locks.  51. 

33.  Tie  Plates. 

34.  Eail  Braces.  52. 

35.  Tie  Straps.  53. 

36.  Detector  Bars.  54. 

37.  Adjustments.  55. 

38.  Signals — General.  56. 

359 


Accidents. 
Patents. 
Payments. 
Contract. 


Obstacles. 

Traffic. 

Completion. 

Provided   by   Purchaser. 

Tenders. 


Dwarf  Signals. 
High  Signals. 
Bridge  Signals. 
Wire  Lines. 
Wire. 

Chain  Wheels. 
Wire   Carriers. 
Wire  Eyes. 
Split    Links. 
Chain. 
Lamps. 
Pins. 

Bolts,  Screws,  and  Wash- 
ers. 

Shore  Foundations. 
Concrete  Foundations. 
Concrete. 
Painting. 
Boxing. 


3«0  APPENDIX. 

GENEKAL. 

1.  Specifications. 

Adherence. — All  the  work  herein  outlined  is  to  be  done  in 
strict  accordance  with  the  specifications,  the  accompanying 
plans  and  such  instructions  as  may  be  given  from  time  to 
time  by  the  purchaser. 

Spirit. — The  nature  and  spirit  of  these  specifications  are  to 
provide  for  the  work  herein  enumerated  to  be  fully  completed 
in  every  detail  for  the  purpose  designed;  and  it  is  hereby 
understood  that  the  contractor  in  accepting  the  contract 
agrees  to  furnish  any  and  everything  obviously  necessary  for 
such  construction. 

Special  Work. — The  purchaser  will  furnish  a  description 
and  drawings  of  all  special  work. 

Copies. — Duplicate  copies  of  these  specifications  will  be 
furnished  by  the  purchaser  with  request  for  tender. 

2.  Drawings. 

Preliminary. — The  purchaser  will  furnish  with  each  copy 
of  the  specifications,  copies  of  all  drawings  in  dictating  the 
work  to  be  performed. 

The  contractor  shall  examine  these  drawings,  call  the  pur- 
chaser's attention  to  any  apparent  errors  and  ascertain  the 
purchaser's  wishes  regarding  the  same  before  submitting  a 
tender. 

Final. — After  the  contract  has  been  awarded,  the  con- 
tractor shall  submit  three  (3)  sets  of  drawings  showing  the 
proposed  arrangement  or  construction,  which  require  the  pur- 
chaser's approval,  one  set  of  which  will  be  approved  and 
promptly  returned.  Should  changes  in  these  drawings  be 
necessary  to  meet  the  requirements  of  the  specifications,  one 
set  will  be  promptly  returned  with  such  changes  indicated  in 
writing,  and  the  contractor  may  proceed  with  the  work  when 
such  corrections  have  been  made. 

The  contractor  shall  furnish  four  (4)  sets  of  working 
drawings  for  the  purchaser's  files  and  upon  request  two  (2) 
additional  sets  for  the  file  of  each  other  interested  company. 

Suitable  framed  manipulation  chart  and  track  diagrams 
shall  be  furnished  in  place  by  the 

3.  Supervision. 

Supervision. — All  work  shall  be  under  the  supervision  of 
the  purchaser's  accredited  representative  hereinafter  referred 
to  as  the  supervisor. 

Foreman. — :The  foreman  of  installation,  and  his  men,  shall 
be  satisfactory  to  the  supervisor. 

Instructions. — 'The  foreman  of  installation  shall  receive 
and  act  upon  all  instructions  given  by  the  supervisor  in 
writing. 


APPENDIX.  361 

3.  Supervision. 

Inspection. — All  material  and  workmanship  will  be  in- 
spected thoroughly  and  carefully,  and  the  contractor  will  be 
held  at  all  times  to  the  spirit  of  the  specifications. 

The  supervisor  shall  be  given  free  access  to  all  parts  of  the 
work  during  the  process  of  construction. 

*The  purchaser  will  make  a  final  inspection  and  tests  with- 
in three  (3)  days  after  the  completion  of  the  work.  Any  de- 
fects or  omissions  noted  during  this  inspection  shall  be  made 
good  by  the  contractor  without  extra  charge  before  the  work 
will  be  accepted. 

Defective  Work. — The  contractor,  upon  being  so  directed 
by  the  purchaser,  shall  remove,  rebuild,  or  make  good,  with- 
out charge,  any  defective  work. 

^Acceptance. — The  purchaser  will  issue  written  acceptance 
of  the  plant  as  soon  as  his  inspection  has  shown  that  all 
work  has  been  completed  in  conformity  with  plans  and 
specifications. 

4.  Alterations. 

Specifications. — The  purchaser  reserves  the  right  to  make 
changes  in  plans  and  specifications.  All  such  changes  shall 
be  handled  in  the  same  manner  as  the  originals. 

*Alterations  involving  a  change  in  the  plans  which  will 
increase  or  decrease  the  amount  of  material  to  be  furnished, 
or  work  to  be  performed  by  the  contractor,  shall  be  classed 
as  extras,  and  such  allowances  shall  be  made  as  may  be  mu- 
tually agreed  upon  in  writing. 

5.  Permits. 

The  purchaser  will  obtain  all  necessary  permits.  Work 
requiring  permits  shall  not  be  prformed  until  same  have 
been  provided. 

6.  Accidents. 

Precaution. — The  contractor  shall  place  sufficient  and 
proper  guards  for  the  prevention  of  accidents  and  shall  put 
up  and  maintain  at  night  suitable  and  sufficient  lights,  as 
specified  in  Article  16. 

Eesponsibility. — The  contractor  shall  save  the  purchaser 
harmless  and  relieve  him  from  all  responsibility  for  any 
damage,  injury,  or  loss  suffered  by  any  person  or  persons  in 
the  employ  of  the  contractor  while  such  person  or  persons 
are  engaged  in  the  construction  of  interlocking,  unless  such 
damage,  injury,  or  loss  is  caused  by  the  negligence  of  the 
purchaser. 

7.  Patents. 

*Patent  Eoyalties. — The  contractor  will  pay  all  patent 
royalties  on  patented  articles  furnished  by  him,  and  will 


362  APPENDIX. 

protect  the  railroad  company  from  all  patent  right  claims. 

8.  Payments. 

*First  Payments. — The  purchaser  will  pay  . .  per  cent  of 
the  contract  price  upon  the  receipt  of  the  material  at  des- 
tination. 

*Second  Payment. — The  remaining  . .  per  cent  of  the  con- 
tract price  will  be  paid  within  . .  days  after  the  acceptance 
of  the  plant. 

*Extras. — Payments  for  extras  will  be  made  in  the  same 
manner  as  prescribed  for  in  the  contract  price. 

9.  Contract. 

As  soon  as  possible  after  the  award  is  made,  the  contract, 
in  accordance  with  the  accompanying  form,  will  be  presented 
in  duplicate  to  the  contractor  for  his  signature,  after  which 
both  copies  will  be  signed  by  the  purchaser  and  one  of  them 
will  be  returned  to  the  said  contractor. 

DETAIL. 

10.  Intent. 

The  intent  of  this  specification  is  to  clearly  describe  all  of 
the  material  and  labor  required  for  and  the  results  to  be  ob- 
tained by  the  complete  installation  of  a  mechanically  oper- 
ated interlocking  plant  at  on  the  lines  of  the 

Kailroad,  as  shown  in  the  plans  and  supplementary 

data  hereto  attached. 

Eesults.  Note. — This  space  is  provided  for  a  complete 
general  description  of  the  plant  and  all  its  adjuncts,  and  of 
the  operating  results  to  be  obtained  therefrom. 

11.  Supplementary  Data. 

Practice. — The  contractor's  recognized  best  practice  shall 
govern  except  as  herein  otherwise  provided.  The  plans, 
drawings,  and  detail  specifications  attached  to  and  forming 
a  part  of  this  specification  are: 


12.  Material  and  Workmanship. 

When  it  is  necessary  or  desirable  to  use  apparatus  not 
heretofore  in  use,  the  contractor  shall  submit  drawings  of 
the  same  with  his  proposal,  and  the  acceptance  of  such  pro- 
posal shall  constitute  acceptance  of  such  new  devices. 

All  material  and  workmanship  shall  be  first  class  in  every 
respect. 
12.  Material  and  Workmanship. 

*The  contractor  shall  furnish  for  replacement  free  on  board 
at  works  any  apparatus  or  material  of  his  own  manufacture 
or  furnished  on  his  own  specifications,  which  shall  prove  de- 


APPENDIX.  863 

fective  after  having  been  in  service  one  year  or  less,  pro- 
vided it  was  used  for  its  intended  purpose. 

The  contractor's  standard  apparatus  shall  be  used,  except 
as  herein  otherwise  specified. 
13.  Transportation. 

The  purchaser  will furnish  transportation  for  the 

men  engaged  in,  and  necessary  tools  and  material  required 
by,  the  installation  of  the  plant  over  the  following  railway 
lines: 


Shipment  and  Handling. — Tools  and  material  are  to  be 
shipped 

To 

Care  of 

At    

Via    

Marked    

Freight  Prepaid  to 

The  purchaser  will  unload  and  properly  house  only  such 
material  as  arrives  before  the  contractor's  men. 

The  use  of  the  following  cars  will  be  permitted  under  the 
restrictions  and  conditions  of  Articles  Nos.  6  and  16,  unless 
otherwise  indicated  in  this  paragraph: 

Number.  Furnished  by 

Motor  cars  

Velocipede  cars  

Hand  cars  

Push  cars  ,         

When  contractor  is  not  permitted  to  use  hand  cars  or  push 
cars,  the  purchaser  will,  at  its  own  expense,  distribute  all 
material  to  the  point  of  use  upon  receipt  of  notification  from 
and  under  supervision  of  contractor's  foreman. 

When  contractor  shall  call  upon  the  purchaser  for  the  re- 
quired number  of  cars  for  the  return  of  tools  and  unused 

material,  and  same  will  be  furnished  in days,  after 

which  time  the  purchaser  will,  at  his  own  expense,  care  for 
and  load  all  tools  and  material. 
14.  Track  Work. 

The  purchaser  will  furnish: 

All  switches,  derails  and  movable  point  frogs  in  place  ad- 
justed to  the  required  throw. 

All  ties  in  place  for  the  support  of  the  apparatus. 

All  rail  braces,  and  will  install  all  except  those  located  on 
tie  plates  furnished  by  the  contractor. 


364  APPENDIX. 

The  purchaser  will  move  all  ties  which  interfere  with  in- 
stallation of  the  interlocking  apparatus  or  connections. 

The  purchaser  will  remove  all  guard  rail  clamps,  rail 
braces,  anti-creepers  and  lips,  and  otherwise  prepare  the  rail 
for  the  installation  of  detector  bars. 

The  purchaser  will  remove  and  replace  all  switch  and  tie 
rods  (other  than  front  rods  on  interlocked  switches)  requir- 
ing a  change  in  location,  the  application  of  insulation,  adjust- 
ment brackets  or  other  alterations. 

15.  Obstacles. 

The  purchaser  will  do  all  preliminary  grading,  provide  ade- 
quate drainage,  and  blast  and  remove  all  solid  rock  that  will 
interfere  with  the  placing  of  the  interlocking  apparatus  or 
connections. 

*Where  it  is  necessary  to  make  an  alteration  or  move  any 
part  of  an  existing  structure,  the  same  will  be  done  by  the 
purchaser. 

16.  Traffic. 

The  contractor  shall  not  unnecessarily  delay  or  interfere 
with  traffic.  When  it  becomes  necessary  for  contractor  to 
perform  any  work  which  may  endanger  traffic,  the  contractor 
shall  notify  the  purchaser  and  shall  not  proceed  with  said 
work  until  traffic  is  protected. 

The  purchaser  will  promptly  arrange  to  protect  traffic  upon 
request  of  contractor. 

17.  Completion. 

The  contractor  shall  notify  the  purchaser,  in  writing,  not 
less  than  seven  (7)  days  before  the  plant  will  be  ready  for 
service. 

The  contractor  shall  put  the  plant  in  service  under  the 
supervision  of  the  purchaser,  and  shall  leave compe- 
tent men  on  duty  for  hours  thereafter. 

The  purchaser  will  maintain  and  operate  the  plant  as  soon 
as  it  is  put  in  service. 

The  purchaser  will  put  the  plant  in  service,  providing  this 
cannot  be  done  within  three  (3)  days  after  the  completion 
of  the  contractor's  work. 

The  contractor  shall  remove  and  dispose  of  all  excess 
earth  and  all  refuse  made  by  the  contractor's  men  or  shall 
load  on  cars,  where  disposal  cannot  be  made  on  right  of  way 
within  interlocking  limits. 

18.  Provided  by  Purchaser. 

a  

b  

c  

d  

e  


APPENDIX.  365 

Note. — Items  to  be  provided  by  purchaser  shall  be  as- 
sembled and  filled  in  at  this  point. 

19.  Tenders. 

Sealed  tenders  for  the  work  covered  by  these  specifications 
will  be  received: 
by 

at     

up  to  hour  on  the  ....  day  of  month 

of  ,  at  which  time  and  place  said  tenders 

will  be  opened.  Bidders  are  invited  to  be  present. 

Note. — This  space  is  provided  for  a  complete  description  of 
the  division  of  the  tenders  for  the  different  portions  of  the 
work. 

a    

b    

c    

d    

The  purchaser  reserves  the  right  to  reject  any  and  all  bids. 

20.  Interlocking  Stations. 

A  building  stories  high  and  

x inside  dimensions,  with  a frame  for  sup- 
porting the  machine,  shall  be  built  by  the  in  ac- 
cordance with  specifications  and  drawings  No for  build- 
ing and  drawings  No for  frame. 

A  foundation  for  the  building  and  leadout  sup- 
ports shall  be  built  by  the in  accordance  with  speci- 
fications and  drawings  No Leadout  supports  shall  be 

furnished  in  place  by  the  accordance  with  draw- 
ings No 

21.  Machine. 

(a)  It    shall    be    of   the   preliminary   latch-locking   type; 
levers  shall  be  numbered  from  left  to  right,  like  parts  of  ma- 
chine of  same  type  shall  be  interchangeable,  and  all  bolts 
shall  be  provided  with  jamb  or  lock  nuts. 

(b)  All  levers  shall  be  arranged  so  that  they  can  be  re- 
moved without  interfering  with  other  levers. 

(c)  Levers  shall  be   ft in.  in  length  from 

end  of  lever  handle  to  center  pin,  and  center  pins  snail  be 
one  and  one-quarter   (l1^,)    in.  in  diameter. 

(d)  All  levers  shall  have  equal  and  uniform  throw,  and 
shall  be  so  arranged  that  connections  may  be  made  to  front 
or  back  of  lever.     Tail  levers  for  pipe  connections  shall  be 
drilled  to  provide  for  eight  and  three-quarter  (8%)  in.,  nine 
and    three-quarter     (9%)     in.    and    ten    and    three-quarter 
(10%)  in.  stroke.     Tail  levers  for  wide  connections  shall  be 
drilled  for  eight  and  three-quarter     (8%)  in.,  ten  and  three- 
quarter    (10%)    in.,    twelve    and    three-quarter    (12%)    in., 


366  APPENDIX. 

fourteen  and  three-quarter  (14%)  in.,  and  sixteen  and  three- 
quarter   (16%)   in.  stroke. 

(e)  One  lever  shall  operate  not  more  than  one  signal,  two 
pairs  of  switch  points,  one  hundred  and  six  (106)  ft.  of  de- 
tector bars  at  single  switches,  or  one  hundred  and  fifty-six 
(156)  ft.  at  slip  switches,  four  rail  locks,  one  switch  and  lock 
movement,  two  bridge  locks,  or  two  eight   (8)    way  bridge 
couplers. 

(f)  Provision  shall  be  made  for  one  tappet  or  cross-lock- 
ing bar,  one  lever  shoe  pin  and  caps,  and  one  locking  bar  ex- 
tending full  length  of  the  machine  for  each  lever  or  space. 

(g)  The  locking  shall  be  distributed  as  uniformly  as  pos- 
sible in  the  locking  bed. 

(h)     Locking  shafts  on  S.  &  F.  type  shall  extend 

ins.  out  from  back  rail  and  shall  be  drilled ins.  from 

end  of  applying  electric  locks,  holes  shall  be ins.  in 

diameter  and  horizontal  with  levers  on  center. 

(i)     The    front,    back    and    intermediate    rails    supporting 
locking  bed  of  S.  &  F.  type  shall  be  provided  with  one  way 
caps. 
22.  Leadout. 

(a)  Eocking  shaft,  deflecting  bar,  or  a  combination  of  de- 
flecting bar  and  vertical  crank  leadout,  shall  be  furnished. 

(b)  Kocking  shafts  shall  be  made  from  two  (2)  in.  square, 
rolled  steel  with  movable  bearings  and  movable  crank  arms. 

Straight  and  bent  shaft  arms  shall  be iron,  eleven 

and  three-quarters  (11%)  ins.  long,  center  to  center.     Kock- 
ing shaft  bearings  shall  be  so  arranged  that  both  ends  of  all 
rocking  shafts  shall  be  supported,  and  no  more  than  six  (6) 
ft.  of  rocker  shaft  shall  be  unsupported. 

(c)  Eocker  shaft  stands  shall  be  made  of  cast  iron,  center 
of  bearing  to  the  base  of  stand  shall  be  fifteen   (15)   ins., 
bases  of  stands  shall  be  symmetrical  and  shall  be  cored  for 

four  (4)  three-quarter  (%)  in.  bolts  spaced x 

in.  centers.     Bearings  shall  be  provided  with  one   (1)   way 
caps  and  shall  be  attached  to  stands  with  two  (2)  five-eighth 
(%)   in.  bolts. 

(d)  Vertical  leadout  chain  wheels  shall  be  made  of  mal- 
leable iron  and  shall  be  ten   (10)   ins.  in  diameter.     Stands 
for  vertical  chain  wheels  shall  be  drilled  for  bearings  ten 
(10)  ins.  and  twelve  (12)  ins.  above  base  of  bearing;  bases 

shall  be  cored  for  two  (2)  three-quarter  (%)  in.  bolts 

in.  centers. 

(e)  All  leadout  appliances  shall  be  securely  fastened  to 
leadout  supports  by  three-quarter   (%)   in.  bolts,  bolt  heads 
shall  be  placed  underneath. 

(f)  All  down  rods  shall  be  vertical  with  offset  jaws,  so 


APPENDIX.  367 

that  they  may  be  connected  to  lever  for  either  eight  and 
three-quarter  (8%)  in.  or  nine  and  three-quarter  (9%)  in. 
stroke,  and  shall  be  connected  to  the  eight  and  three-quarter 
(8%)  in.  stroke  hole. 

(g)  Shackles  shall  be  connected  to  tail  levers  with  stand- 
ard seven-eighth  (%)  in.  by  two  and  one-quarter  (2:V4)  in. 
pins  for  all  wire  lines,  and  sufficient  movement  of  wire  line 
shall  be  provided  to  successfully  operate  all  wire  connected 
signals. 
23.  Pipe  Line. 

(a)  One    inch    pipe    shall    be    used    for    connections    to 
switches,   derails,   movable   wing   and   point   frogs,    detector 

bars,   locks,   bridge   couplers,   and   high   home   and    

signals. 

(b)  Pipe  lines  shall  be  straight  where  possible  and  shall 
not  be  placed  less  than  four  ft.  six  in.  (4'  6")  from  gage  line, 
except  where  the  line  runs  between  tracks  or  permission  is 
granted  by  the  purchaser.     On  draw  spans  and  approaches 
they  shall  be  kept  as  far  from  the  gage  line  as  conditions  will 
permit. 

(c)  Where  possible  pipes  in  main  pipe  line  shall  be  run 
so  that  they  will  lead  off  on  track  side  in  regular  order. 

(d)  Top   of  pipe   carrier  foundations   in   main  pipe   line 
shall  be  one  (1)  in.  below  base  of  rail  where  conditions  will 
permit. 

(e)  All  cranks,  compensators,  and  deflecting  bars  in  main 
pipe  run  shall  be  so  located  as  to  leave  field  side  clear  for 
wires,  trunking  and   additions. 

(f)  Pipe  lines  shall  be  laid  two  and  three-quarters  (2%) 
ins.  between  centers  and  shall  be  supported  on  pipe  carriers 
placed  not  more  than  seven    (7)    ft.  centers.     The  distance 
from  base  on  which  pipe  carriers  are  supported  to  the  center 
of  pipe  line  shall  be  four  and  one-quarter  (434)  in. 

(g)  Couplings  in  pipe  lines  shall  be  located  not  less  than 
twelve  (12)  in.  from  pipe  carriers  with  lever  on  center. 

(h)  Where  so  specified  on  plans  at  points  where  pipe  lines 
cross  under  tracks,  roads,  platforms,  etc.,  standard  one  (1)- 
in.  pipe  shall  be  run  inside  of  standard  two  (2)  in.  galvanized 
iron  pipe,  provided  at  each  end  with  a  stuffing  box,  which 
shall  be  provided  with  an  oil  inlet,  and  shall  be  attached  to 
the  pipe  by  standard  pipe  coupling.  Design  shall  be  such  as 
to  permit  of  standard  spacing  of  pipe  lines  two  and  three- 
quarters  (2%)  in.  between  centers. 

(i)  Where  so  specified  I-beam  track  supports  shall  be  used 
where  pipe  lines  cross  under  tracks,  and  I-beam  construction 

shall  be  built  as  per  plan  No attached,  and  shall 

be  furnished  and  put  in  place  by  the  Purchaser. 


368  APPENDIX. 

(j)  Except  where  otherwise  provided,  pipe  lines  run 
across  tracks  shall  be  arranged  to  permit  standard  spacing 
and  proper  tamping  of  ties. 

(k)  Pipes  leading  across  tracks  shall  be  supported  by 
transverse  pipe  carriers  fastened  to  top  of  ties  where  prac- 
ticable. 

(1)     Turns  in  pipe  line  shall  be  made  witn  radial  arms, 
cranks,  or  deflecting  bars  as  follows: 
(m)     Angle  of  Deflection: 

0       degrees  to     11       degrees 
11       degrees  to     33%  degrees 
33%  degrees  to     56       degrees 
56       degrees  to     78%  degrees 
78%  degrees  to     90       degrees 
0       degrees  to     30       degrees 
30       degrees  to     75       degrees 
75       degrees  to  105       degrees 
105       degrees  to  140       degrees 
140       degrees  to  180       degrees 
Deflecting  bars  with  tang  ends: 
22%  degrees  deflecting  bars  with  eye  ends. 
45       degrees  deflecting  bars  with  eye  ends. 
67%  degrees  deflecting  bars  with  eye  ends. 
90       degrees  deflecting  bars  with  eye  ends. 
15       degrees  radial   arm   cranks. 
60       degrees  acute  angle  cranks. 
90       degrees  standard  cranks. 
120       degrees  obtuse  angle  cranks. 
180       degrees  equalizing  arms. 

(n)  Pipe  lines  shall  be  installed  in  accordance  with  tem- 
perature diagram,  and  table  of  equivalent  lengths  used  in 
compensating  pipe  lines  when  crank  arms  are  of  unequal 
length. 

(o)  Deflecting  bars,  radial  cranks,  pipe,  stuffing  boxes, 
tang  ends,  plugs,  and  couplings  shall  be  Eailway  Signal  Asso- 
ciation Standard. 

(See  specifications  for  1-in.  pipe  couplings.) 
24.  Pipe  Carriers. 

(a)  Pipe  carriers  for  main  pipe  runs  shall  be  of  the  anti- 
friction type,  and  constructed  of  individual  sides,  top  and 
bottom  rollers;  sides  shall  be  connected  together  at  top;  and 
in  contact,  but  not  connected  at  bottom;  bases  shall  be  cored 
for  two  (2)  one-half  (%)  in.  lag  screws in.  cen- 
ters, and  fastened  to  foundations  with  two  (2)  x 

in.  lag  screws. 


APPENDIX.  369 

(b)  Transverse  carriers  shall  be  constructed  of  individual 
sides,  top  and  bottom  rollers,  sides  shall  be  supported  by  a 
wrought  or  malleable  iron  bearer,  and  connected  together  by 
a  one-half  (%)  in.  pin  through  center  of  bottom  roller,  con- 
nected to  bearer,  with  one-half  (%)  in.  bolts,  and  fastened  to 
foundations  with  two  (2)  three-quarter  (%)  by  four  (4)  in. 
lag  screws. 

(c)  The  pipe  carrier  shall  be  constructed  of  malleable  or 
wrought  iron  frame  and  bottom  roller,  assembled  together  by 
one-half  (^)  in.  pin  through  center  or  roller,  and  fastened  to 
foundation  with  two   (2)  one-half  (^)  in.  by  two  and  one- 
half  (2%)  in.  lag  screws. 

(d)  All  pipe  carrier  sides  and  bottom  rollers  shall  be  made 
of  malleable  iron. 

25.  Compensation. 

(a)  Compensation  shall  be  provided  for  all  pipe  connected 
units  or  apparatus  where  same  is  necessary  to  insure  proper 
operation. 

(b)  Unless  compensation  is  otherwise  provided  for,  a  lazy 
jack  compensator  shall  be  provided  for  each  pipe  line  over 
fifty  (50)   ft.  in  length  and  under  eight  hundred  (800)   ft., 
with  crank  arms  ten  by  thirteen  (10x13)  in.  centers.     From 
eight  hundred  (800)  to  twelve  hundred  (1,200)  ft.  in  length, 
crank  arms  shall  be  ten  by  sixteen  (10x16)  in.  centers.    Pipe 
lines  over  twelve  hundred  (1,200)  ft.  in  length  shall  be  pro- 
vided with   additional   compensators.     No   more  than   seven 
hundred  and  twenty-five  (725)  ft.  of  pipe  shall  be  compen- 
sated by  an  eleven  and  three-quarter  (11%)  by  eleven  and 
three-quarter  (11%)  in.  crank. 

(c)  No   more    than    one   horizontal   compensator   or  two 
vertical  compensators  shall  be  mounted  in  one  stand. 

(d)  Compensators  shall  have  one  (1)   sixty  (60)   degree 
and  one   (1)   one  hundred  and  twenty  (120)   degrees  angle 
cranks,  with  bosses  two   (2)   in.  thick,  and  eleven   (11)   in. 
connecting  link,  mounted  in  cast  iron  bases,  having  top  of 
center  pin  supported.     The  distance  between  center  of  pin 
holes  shall  be  twenty-two  (22)  in.,  and  bases  shall  be  cored 

for  four  (4)  three-quarter  (%)  in.  bolts  spaced 

x in.  centers. 

26.  Horizontal  Cranks. 

Cranks  shall  be  made  of  wrought  iron  and  drilled  eleven 
and  three-quarters  by  eleven  and  three-quarters  (ll%xll%) 
in.  center  to  center,  with  boss  two  (2)  in,  thick.  They  shall 
be  mounted  in  cast  iron  bases,  having  top  of  center  pin  sup- 
ported. Not  more  than  two  (2)  cranks  shall  be  mounted  in 


370  APPENDIX. 

the  same  base,  and  no  more  than  one  crank  mounted  on  one 
center.  Bases  shall  be  cored  for  four  (4)  three-quarter  (%) 
in.  bolts,  spaced x ,  in.  centers. 

27.  Vertical  Cranks. 

Cranks  shall  be  made  of  wrought  iron  and  drilled  eleven 
and  three-quarters  by  eleven  and  three-quarters  (ll%xll%) 
in.  center  to  center,  with  boss  two  (2)  in.  thick.  They  shall 
be  mounted  in  one  and  two  way  cast  iron  stands  and  drilled 

for  bearings   in  centers  above  base,  and  base 

cored  for  four  (4)  three-quarter  (%)  in.  bolts,  spaced 

x   in.  centers. 

28.  Switch  and  Lock  Movement. 

Switch  and  lock  movement  shall  be  securely  bolted  to  five- 
eighth  by  twelve  by ft.  (%"x!2"x ') 

iron  plates,  and  shall  be  placed  on  outside  of  track 

ft in.  from  gage  of  nearest  rail  bolted  to  ties. 

29.  Deflecting  Bars. 

(a)  Deflecting  bars  shall  be  made  in  one  way  multiple 
unit  type;  bars  shall  be  made  of  one  and  one-quarter  (1%) 
in.  square  steel,  and  designed  for  ten   (10)   in.  stroke,  and 
shall  be  bent  at  the  following  radii: 

22y2  degree,  radius  seventy-two    (72)    in. 
45       degree,  radius  thirty-six   (36)   in. 
671/2  degree,  radius  twenty-four  (24)  in. 
90       degree,  radius  eighteen   (18)   in. 

(b)  All  cranks,  compensators,  deflecting  bars,  switch  and 
lock  movement,  and  stands  shall  be  Railway  Signal  Associa- 
tion Standard. 

30.  Jaws  and  Lugs. 

(a)  Except  where  otherwise  specified,  solid  jaws  shall  be 
used  for  connections  to  all  cranks,  compensators,  deflecting 
bars,  couplers,  rail  locks,  pipe  connected  levers,  and  balance 
levers. 

(b)  The  body  of  all  jaws  shall  be  of  wrought  iron,  one 
and  eleven  thirty-seconds  (1  11/32)  in.  in  diameter,  with  tang 
and  thread  for  coupling  to  pipe. 

(c)  The  sides  of  solid  jaws  shall  be  parallel  for  three  (3) 
in.  from  center  of  pin  hole,  and  length  of  solid  jaws  shall  be 
nineteen  and  one-half  (19%)  in.  from  center  of  pin  hole  to 
center  of  first  rivet  hole. 

(d)  Screw  jaws  shall  be  used  as  follows:   one  for  each 
switch  connection  to  bolt  lock,  front  rod,  lock  rod,  switch  and 
lock  movement,  detector  bar  connection,  in  signal  line  on  each 
side  of  bolt  lock,  and  in  each  high  signal  down  rod,  and  shall 
be  located  as  close  as  possible  to  the  unit  to  be  adjusted. 

(e)  Screw  jaws  shall  be  made  of    iron,  with 


APPENDIX.  371 

hexagon  shank  ends  the  same  size  as  the  outside  dimension 
of  the  one  and  one-quarter  (1*4)  in.  standard  jamb  nuts. 

(f)  The  sides  of  screw  jaws  shall  be  parallel  for  five  (5) 
in.  from  center  of  pin  holes,  and  length  of  screw  jaw  shall  be 
nineteen  and  one-half  (19%)  in.  from  center  of  pin  hole  to 
center  of  first  rivet  hole  with  shank  of  jaw  on  center  of 
thread. 

(g)  Each  screw  jaw  shall  be  provided  with  jamb  nut. 
(h)     Pipe   lugs   shall  be   made   of  wrought  iron   one  and 

eleven  thirty-seconds  (1  11/32)  in.  in  diameter,  fitted  with 
thread  and  tangs  for  coupling  to  pipe,  and  minimum  dis- 
tance from  center  pin  hole  to  center  of  first  rivet  hole  shall 

be   in. 

(i)  All  jaws,  lugs  and  tangs  shall  be  Kailway  Signal  As- 
sociation Standard. 

31.  Offsets. 

Offsets  in  pipe  lines  shall  be  made  in  body  of  jaws,  or  in 
iron  rod  one  and  eleven-thirty-seconds  (1  11/32)  in.  in  diam- 
eter. The  total  offset  between  any  two  supports  shall  never 
exceed  three  and  one-half  (3^)  in.,  minimum  distance  be- 
tween ends  of  offset  shall  never  be  less  than  twice  the 
amount  of  the  offset.  Offsets  in  cranks  and  compensators 
shall  be  avoided  as  far  as  possible. 

32.  Locks. 

(a)  Facing  point  locks  shall  be  used  on  all  switches,  de- 
rails, movable  wing  and  point  frogs,  except  where  otherwise 
specified    on    plans.      Locks    shall    be    arranged    to    lock    all 
switches  in  normal  and  reverse  position,  and  all  derails  in 
reverse  or  closed  position  only. 

(b)  Facing  point  lock  stands  shall  be  placed  on  outside  of 
track,   twenty-eight    (28)    in.    from   gage   and  bolted   to   tie 
through  a  tie  plate,  placed  on  top  of  tie,  and  tie  plate  shall 
extend  under  and  support  the  nearest  rail  and  point.    Facing 
point  lock  stands  shall  be  arranged  to  support  the  plunger  on 
each  side  of  lock  rod  to  support  the  lock  rod  on  each  side  of 
the   plunger,   and  bases   shall  be   cored   for  four    (4)    three- 
quarter    (%)    in.   bolts x in.   centers. 

(c)  Facing  point  lock  plungers  shall  be   one    (1)   in.  in 
least   dimension,  with  square  end  and  nineteen    (19)   in.  in 
length  from  center  of  pin  hole  to  end,  have  full  stroke  of 
pipe  line,  and  stand  one  (1)  in.  clear  of  lock  bar  when  switch 
is  unlocked. 

(d)  Lock  rods  shall  run  direct  from  front  rods  into  lock 
stands,  and  shall  be  of  the  double  adjustable  type.    Holes  or 
notches  in  lock  rods  shall  have  square  edges  and  shall  not  be 
more  than  one-sixteenth  (1/16)   in.  larger  than  plunger. 

(e)  When    electric   locking   or   switch   circuit   controllers 


372  APPENDIX. 

are  not  used,  all  facing  point  switches,  movable  wing  and 
point  frogs  on  high  speed  routes  shall  be  bolt  locked  with 
signals  governing  such  routes;  and  all  facing  derails  shall  be 
bolt  locked  with  all  signals  governing  over  them. 

(f)  All  bolt  lock  stands  shall  be  made  in  one   (1)  way 
multiple  unit  type,  and  cored  for  four  (4)  three-quarter  (%) 
in.  bolts. 

(g)  Switch  bar  in  bolt  lock  shall  be  made  of  mild  steel 

x with in.  notch,  and 

have   an  independent   connection  to  switch  point  and  shall 
not  be  connected  to  front,  lock,  throw  rods,  or  point  lugs,  if 
front  rod  is  attached  to  them. 

(h)  Signal  bar  in  bolt  lock  shall  be  made  of  mild  steel 

x with in.  notch,  and 

be  a  part  of  the  pipe  line,  and  not  lugged  or  looped  in. 

(i)  Lock  stands,  plungers,  front  rods,  lock  rods,  and 
switch  lugs  shall  be  Eailway  Signal  Association  Standard. 

Note. — Where  local  conditions  are  such  that  it  is  not  prac- 
ticable to  install  bolt  locking  the  committee  recommends  cir- 
cuit controllers  on  switches,  derails,  movable  wing  and  point 
frogs,  and  their  respective  operating  levers  with  electric  locks 
on  lock  levers  to  insure  that  switches  have  responded  to  the 
position  of  the  lever,  or  where  slotted  signals  are  used,  they 
shall  be  controlled  by  circuit  controllers  on  switches,  derails, 
movable  wing  and  point  frogs. 

33.  Tie  Plates. 

(a)  Three  tie  plates  shall  be  used  for  all  switches  and 
derails,  and  shall  be  located  as  follows:  one  on  point  tie,  and 
one  on  nearest  tie  on  either  side.     Four  tie  plates  shall  be 
used  for  each  set  of  movable  point  frogs,  and  shall  be  lo- 
cated as  follows:  one  on  point  tie,  and  one  on  first  tie  back 
of  the  point  tie  for  each  pair  of  points. 

(b)  Tie  plates  shall  be  one-half  in.  by  six  in.  by „ 

(I"x6"x ) ;  butt  plates  shall  be   x 

x and  drilled  for in. 

rivets.     Riser  plates  shall  be x x 

and  drilled  for in.  rivets.    All  tie 

plates  shall  be  fitted  in  place  and  securely  fastened  to  the 

ties  with  three-quarter  by  four  (%x4)  in.  lag 

screws. 

34.  Bail  Braces. 

Eail  braces  shall  be  furnished  by  the  Purchaser. 

35.  Tie  Straps. 

(a)  At   all   switches,    derails,   movable   wing   and   point 
frogs,  tie  straps  shall  be  used,  to  tie  all  crank,  rocker  shaft, 
point  and  intermediate  ties  together. 

(b)  Tie   straps  shall  be  one-half   by  two   and   one-half 


APPENDIX.  373 

(%*2%)  in.  iron,  placed  on  top  of  ties  and  fastened  to  the 
ties  with  three-quarter  by  four  (%x4)  in.  lag  screws. 
36.  Detector  Bars. 

(a)  Bars  shall  be  located  as  shown  on Plan 

No date  attached  hereto,  unless 

otherwise  specified. 

(b)  Bars  on  curves  shall  be  located  on  inside,  outside 
or  both   sides   of  curve   as  determined  by  local   operating 
traffic  conditions. 

(c)  Detector  bars  shall  be  arranged  to  give  fifty-three 
(53)    ft.    continuous    protection    for    all    switches,    derails, 
movable  wing  and  point  frogs,  and  shall  lap  the  switch  points 
a  distance  equal  to  the  stroke  of  the  bar. 

(d)  Detector  bars  shall  be  three-eighth  by  two  and  one- 
quarter    (%x2^4,)   in.   steel,   have   one  beveled  edge,  square 
ends,  and  bolted  joints,  and  shall  be  made  up  in  eighteen  ft. 
sections. 

(e)  Bars  shall  be  drilled  one  (1)  in.  from  bottom  of  bar 
to  center  of  hole  for  three  (3)  one-half  (%)  in.  countersunk 
head  bolts  or  rivets.    The  first  hole  shall  be  one  (1)  in.  from 
end   to   center  and   two    (2)    in.  between   centers  of  holes. 

Splice  plates  shall be  used;   they  shall  be  of 

wrought    iron    one-half   by    two    by    twelve    (^x2x!2)    in., 
riveted  at  one  end  of  bar  with  three   (3)   one-half  by  one 
(%xl)    in.   countersunk  head  rivets  and   attached  to  inter- 
mediate sections  by  three  (3)  one-half  by  one  and  one-quarter 
(Msxl^,)  in.  countersunk  head  bolts,  with  nuts  held  in  place 
by  nutlocks. 

(f)  Driving   pieces   shall   be   made    of   wrought   iron   ar- 
ranged for  one  and  eleven  thirty-second   (1  11/32)   in.  jaw 
connections.     The  part  where  the  jaw  is  connected  shall  be 
three-quarters  by  two  by  three   (%x2x3)   in.;  and  part  riv- 
eted to  bar  shall  be  one-half  by  two  by  six  (^x2x6)   in., 
drilled  for   three    (3)    one-half    (^)    in.   rivets;   one    (1)    in. 
from  end  and  two   (2)   in.  between  center  of  holes.     Offset 
from    bar    to    jaw    connection    shall    be    one    and    one-half 

(1%)  in- 

(g)  Driving  pieces  shall  be  placed  midway  between  two 
(2)  clips  in  space  not  equipped  by  joint,  and  the  driving  rod 
shall  have  not  more  than  seven  (7)  ft.  unsupported. 

(h)  Fifty-three  (53)  ft.  bars  shall  be  mounted  on  sixteen 
(16)  type  rail  clips,  and  a  proportionate  num- 
ber of  clips  shall  be  used  for  longer  or  shorter  bars. 

(i)  Centers  of  rail  clips  shall  be  placed  eight  (8)  in.  and 
twenty-six  (26)  in.  respectively  from  each  end,  and  the  re- 
maining clips  approximately  four  (4)  ft.  apart. 

(j)     Where    radial    arm    clips    are    usd    combination    bar 


374  APPENDIX. 

stops  and  guides  shall  be  provided  for  each  ten  (10)  ft.  of 
bar  (equally  spaced),  and  not  less  than  two  (2)  such  stops 
on  one  bar. 

(k)  Bars  shall  be  mounted  substantially  and  operated 
close  to  head  of  rail  in  a  plane  inclined  toward  the  center  of 
track. 

(1)  Bars  shall  rise  a  minimum  of  three-quarters  (%)  in. 
above  top  of  rail  during  the  locking  and  unlocking  of  the 
switch  and  shall  rest  one-quarter  (%,)  in.  below  top  of  rail 
when  lever  movement  is  completed. 

(m)  Where  rocking  shafts  are  used,  they  shall  be  made 
of  two  (2)  in.  rolled  steel  with  movable  bearings  and  crank 

arms.     Arms  shall  be iron  and  nine    (9)   inches 

center  to  center.  The  bearings  shall  be  securely  bolted  to 
ties  with  four  (4)  three-quarter  (%)  in.  bolts.  The  max- 
imum spacing  of  supports  shall  be  six  (6)  ft.  centers. 

(n)     Detector  bar  fittings  shall  be  Eailway  Signal  Asso- 
ciation  Standard. 
37.  Adjustments. 

(a)  Open  turnbuckles  shall  be  placed  in  each  pipe  line 
as   follows:      One    for   each   facing   point   lock,    switch    and 
lock  movement,  pipe  connected  high  home,  dwarf,  or  pot  sig- 
nal;  bridge  lock  and   couplers,  located  as  near  to  the  last 
operated  unit  as  it  is  possible  to  get  them,  without  having 
them  directly  under  the  rails,  guardrails,  frogs,  switches  or 
bridge  guards. 

(b)  Open  turnbuckles  shall  be  made  of iron, 

with  right  and  left  hand  thread,  capable  of  giving  an  adjust- 
ment of  not  less  than  six   (6)   in.,  and  provided  with  hex- 
agon end  shanks,  which  shall  be  the  same  size  as  the  out- 
side diameter  of  the  ore  and  one-quarter  (l^,)  in-  standard 
jamb  nut.     Threaded  rods  shall  be  made  of  one  and  eleven 
thirty-seconds    (1    11/32)    in.    wrought    iron,    provided   with 
standard  tang  ends,  threads  and  couplings. 

(c)  Wire  lines  for  wire  connected  distant  signals  shall  be 
provided  with  two  (2)  adjusting  screws  for  each  wire,  one  in 
the  tower,  and  one  at  base  of  signal  pole. 

(d)  Wire  lines  for  wire  connected  dwarf  signals  shall  be 
provided  with  one    (1)    adjusting  screw  for  each  wire   and 
shall  be  placed  in  the  tower. 

(e)  Wire  adjusting  screws  shall  be  made  of  wrought  iron 
not  less  than  one-half  (%)  in.  diameter  with  right  and  left 
hand  thread,  and  shall  be  capable  of  giving  an  adjustment 
of  twelve  (12)  in. 

(f)  Switches,  derails,  movable  wing  and  point  frogs  shall 
be  provided  with  special  switch  adjustment  fastened  to  the 
head  rod. 


APPENDIX.  375 

(g)     Switches,  movable  wing  and  point  frogs,  and  split 
point  derails  shall  open  not  less  than in. 

38.  Signals. 

(a)  General. — All  signals  shall  be  of  the  semaphore  type 

with  arm  travel degrees  in  the right 

hand  quadrant. 

(b)  Not  more  than  one  arm  shall  be  placed  on  a  dwarf 
signal  post. 

(c)  Not  more  than  three  arms  shall  be  placed  on  a  high 
signal  post,  bridge,  or  bracket  doll. 

(a)  Location. — The  general  type  of  signals  are  shown  in 
the  Eailway  Signal  Association  symbols  and  the  location  of 
signals   shown   shall  be  in   accordance  with   scale  plan  No. 
,  dated revised 

(b)  All  signal  posts  shall  be  on  the  right  of  the  track 
governed,  and  adjacent  thereto  when  possible. 

(c)  The  arms  shall  be  at  right  angles  to  the  track  gov- 
erned   on    tangents,    and    at    right    angles    to    one    thousand 
(1000)  ft.  chord  on  curves,  or  the  total  chord  if  curve  is  less 
than  one  thousand   (1000)   ft.  long. 

(d)  Signals  placed  between  tracks  on  tangents  shall  be 
set    so   that   the    center    of    post   shall   be   midway  between 
tracks.    Signals  placed  between  tracks  on  curves  shall  be  set 
off  the  center  line  between  tracks  and  towards  the  center 
of  the  curve  two  and  one-half  (2%)  in.  for  each  one  (1)  in. 
elevation  in  the  outside  of  the  curve. 

(e)  The   balance  levers   on  wire   connected  high   signals 
located  between  tracks  shall  be  set  parallel  to  tracks. 

(f)  The  contractor   shall  notify  purchaser  if  tracks  are 

less  than   ft.  center  to  center  for  high  signals, 

and    ft.    center   to    center   for    dwarf   signals, 

which  are  shown  between  tracks  or  if  any  signals  are  shown 
within  fouling  limits. 

(g)  Outside  of  tracks,  dwarf  signal  posts  shall  be  placed 

ft.  from  nearest  rail,  high  signal  posts 

ft.  and  bracket  posts   ft. 

(h)     Base   of  dwarf   signals   shall   be   two    (2)    in.   below 

base  of  rail.    Base  of  high  signals  shall  be  in. 

below  base  of  rail. 

39.  Dwarf  Signals. 

(a)  Dwarf  signals  shall  be   position  of  the 

type. 

(b)  Posts  shall  be  made  of  wrought  iron  pipe 

in.  in  diameter   ft in.  from  base 

to  center  of  bearing,  and   ft in. 

from   base    to    center   of    arms.     Arms   shall   be   flexible   or 
hinged,  of in.  x in.  x 


376  APPENDIX. 

in.,  placed  so  that  outer  end  is in.  from  vertical 

line  through  center  of  shaft.    Arms  shall  be  fastened  to  arm 

casting  by  two   (2)   bolts   x   , 

in.  center  to  center  vertically. 

(c)  Arm  casting  shall  be  made  of   iron,  ca- 
pable   of    holding    one    (1)     glass,    one    (1) 

glass,   and   one    (1)    glass,   solid 

color.     Each  glass  shall  be    in.  in  diameter  x 

in.  thick  with  centers in.  from 

center  of  shaft.     Back  lights  will   be  required. 

(d)  Back  light  castings  shall  be  capable  of  holding  one 

(1)   glass,  solid  color.    Glass  shall  be 

in.  in  diameter  x   in.  thick. 

(e)  Semaphore  shaft  shall  be  made  of  cold  rolled  steel 
in.  square. 

(f)  Base   castings  for   dwarf   signals  .shall  be   cored   for 

bolts in.  in  diameter  at  a  radius 

of in. 

40.  High  Signals. 

(a)  High  speed  signals  shall  be position. 

(b)  Medium  speed  signals  shall  be position. 

Low  speed  signals  shall  be position. 

40.  High  Signals — Continued. 

(c)  Straight  pipe  posts  shall  be  made  of  six  (6)  in.,  five 
(5)  in.,  and  four  (4)  in.  wrought  iron  pipe  with  water-tight 
joints,  and  the  size,  weight,  and  length  of  the  wrought  iron 
pipe  shall  be 

Weight 
Item.  Size.       per  ft.     Length. 

Top    section    4  in.         10.66         10  ft. 

Second    section    5  in.         14.56         10  ft. 

Third  section    6  in.         18.76       To  meet  specification 

as  to  length. 

(d)  The  length  of  straight  post  shall  be  as  follows: 

One  arm  24  ft.  6  in. 
Two  arm  31  ft. 
Three  arm  37  ft.  6  in. 

(e)  The   spacing   of   arms   shall  be    as   follows:    distance 
from  top  shaft  to  second  shaft  six   (6)   feet  six  (6)  inches, 
and  from  second  shaft  to  third  shaft  ten  (10)  feet. 

(f)  Posts  shall  be  mounted  in  base  costings.     Base  cast- 
ings shall  be  cored  for  four  (4)  one  (1)  in.  bolts  at  a  radius 
of in. 

(g)  Center  of  arms  shall  be in 

the  center  of  shaft.    Arms  shall  be  made  of , 

in.  x in.  from  vertical  line  through 

center  of  shaft,  and  shall  be  fastened  by   bolts 


APPENDIX.  377 

in.  x . ...  in.  spaced  in 

center  to  center  vertically  and in.  center  to  cen- 
ter horizontally. 

(h)  Arm  castings  shall  be  made  of ,  capable 

of  holding  one  glass,  one glass, 

and  one glass,  solid  color.  Each  glass  shall  be 

in.  in  diameter  x  in.  thick,  with 

centers  in.  from  center  of  shaft.  Back  lights 

will  be  required. 

(i)  Back  light  castings  shall  be  capable  of  holding  one 

glass,  solid  color.  Glass  shall  be  

in.  in  diameter  x  in.  thick. 

41.  Bridge  and  Bracket  Signals. 

(a)  All  bridge  and  bracket  dolls  shall  be  made  of  four 

(4)   in.  pipe,  mounted  in    base  castings.     Base 

castings   shall  be   cored  for   four    (4)    bolts   one    (1)    in.  in 
diameter  at  a  radius  of   in. 

(b)  Top  of  cross-trees  shall  be ft 

in.  above  base  of  bracket  post. 

(c)  Bracket  post  shall  be  made  of  nine  (9)  in.  and  eight 
(8)    in.  wrought  iron  pipe  with  water-tight  joints  mounted 

in   base  castings.     Base  casting  shall  be  cored 

for  four  (4)  bolts  one  and  one-half  (1%)  in.  diameter  at  a 
radius  of   in. 

(d)  Bridge  dolls  shall  be  located  on   chord 

of  bridge. 

(e)  All  signals,  fittings,  and  glass  shall  be  Kailway  Sig- 
nal Association  Standard. 

42.  Wire  Lines. 

(a)  Two  wires  shall  be  used  for  operating  each  wire  con- 
nected signal;  the  normal  operating  wire  shall  have  two  (2) 
in.  more  stroke  than  the  reverse  oprating  wire. 

(b)  Wire  lines  shall  be  carried  in  wire  carriers  placed  not 
more  than  twenty-one  (21)  ft.  apart.     Where  wire  lines  run 
next  to  pipe  lines,  the  wire  carriers  shall  be  attached  to  the 
pipe  carrier  foundations. 

(c)  Where    wire    carriers    are    attached    to    independent 
foundations,  they  shall  be  placed  not  less  than  six   (6)   ft. 
from  gage  of  nearest  rail  where  practicable. 

(d)  Where  wire  lines  lead  around  curves  the  carriers  shall 
be  placed  at  the  proper  angle  to  prevent  wire  leaving  groove 
of  pulley. 

(e)  Turns    in    wire    lines    shall    be    made    around    chain 
wheels  with  a  continuous  piece  of  chain  not  less  than  four 
(4)  ft.  in  length. 

(f )  Where  specified  on  plans,  wires  shall  be  run  inside  of 
three-eighth    (%)    in.   galvanized    iron    pipe    under    tracks, 


378  APPENDIX. 

roads,  platforms,  etc.,  provided  at  each  end  with  a  stuffing 
box  attached  to  the  pipe;  stuffing  boxes  shall  be  provided 
with  oil  inlet. 

43.  Wire. 

Signal  wire  shall  be  hard  drawn,  galvanized  steel  No.  8  B. 
W.  G.  (.165  in.  in  diameter).  The  wire  shall  be  cylindrical, 
free  from  scales,  inequalities,  splices,  and  other  defects.  Each 
coil  shall  consist  of  one  continuous  wire  not  less  than  two 
thousand  (2000)  ft.  in  length  and  five  feet  in  diameter.  A 
single  strand  of  this  wire  shall  be  capable  of  standing  a  load 
of  two  thousand  (2000)  Ibs.,  and  the  elongation  shall  not  ex- 
ceed four  (4)  per  cent,  in  a  length  of  six  (6)  in.  A  specimen 
taken  from  a  coil  must  be  capable  of  standing  four  (4)  close 
turns  around  its  own  diameter. 

44.  Chain  Wheels. 

(a)  Chain  wheels  shall  be  made  of  malleable  iron.     Not 
more  than  two   (2)   shall  be  mounted  in  vertical  line.     The 
diameter  of  wheels  shall  be  ten  (10)  in.,  except  box  wheels 
and  wheels  used  in  dwarf  signal  lines,  which  may  have  a 
minimum  diameter  of  six  (6)  in. 

(b)  Stands  for  chain  wheels  shall  have  top,  bottom,  and 
intermediate  supports.     Distance  between  supports  shall  be 

in.    and    bottom    of    bottom    support    shall   be 

in.  above  base.     Wheels  to  be  assembled  with 

. . . . x   in.  steel  pins.     Bases  shall  be 

cored  for  four  (4)  three-quarter  (%)  in.  bolts 

x in.  centers. 

45.  Wire  Carriers. 

Sheaves  for  wire  carriers  shall  be  two  (2)  in.  in  diameter 
over  all  and  shall  be  made  up  in  two  (2),  four  (4)  and  six 
(6)  ways,  with  no  more  than  two  (2)  sheaves  in  vertical 

line.     Stands  shall  be  drilled  for  bearings in., 

and    in.   above  base   of   bearing.     Bearing  of 

sheaves   shall   be   supported   by    sheaves,   and 

stands  shall  be  made  of  malleable  iron,  and  shall  be  secured 
to  foundation  with  two  (2)  one  and  one-half  (1%)  in.  num- 
ber fourteen  (14)  screw. 

46.  Wire  Eyes. 

Standard  one  and  one-half  (1%)  in.  galvanized  wire  eyes 
shall  be  used  in  making  all  wire  connections. 

47.  Split  Links. 

Split  links  shall  have  three-quarter  (%)  by  one  and  five- 
eighth  (1%)  in.  inside  dimensions  and  be  made  of  five-six- 
teenth (5/16)  in.  galvanized  steel.  After  connections  are 
made  points  shall  be  closed. 

48.  Chain. 

(a)     All  signal  chain  shall  be  made  of  one-quarter 


APPENDIX.  379 

in.  diameter  . .. iron,  and  shall  have  a  maximum  of 

fourteen  (14)  links  to  the  foot.  The  inside  dimensions  of  the 
links  shall  be  thirteen-sixteenths  by  one  and  three-eighths 
(13/16x1%)  in. 

(b)  All  signal  chain  shall  withstand  a  breaking  test  of 
three  thousand  (3000)  Ibs.,  and  the  elongation  shall  not  ex- 
ceed ten  (10)  per  cent.  Test  to  be  made  with  piece  of  chain 
twelve  (12)  ft.  long,  which  shall  show  no  deformation  after 
test.  Any  link  showing  imperfection  under  proof  test  of 
twelve  hundred  (1200)  Ibs.  shall  be  replaced  before  the  chain 
will  be  accepted. 

49.  Lamps. 

Lamps  shall  be  Eailway  Signal  Association  Standard  and 
shall  be  furnished  by 

50.  Pins. 

(a)  All  pins  shall  be  made  of  steel  with  a  permissible 
variance  of  .002  in.  under  size. 

(b)  Center  pins  for  cranks,  compensators,  and  switch  and 
lock  movements  shall  be  interchangeable,  and  shall  be  one 

and  one-quarter   (1^4)   in.  by    in.,  flattened  at 

lower  end  to  enter  an  oblong  hole  in  the  stands  to  prevent 
turning,  with  a  groove  in  upper  end  so  that  they  can  be  easily 
removed,  and  cotter  pin  holes  shall  be  large  enough  to  pre- 
vent shearing  strain  on  one-quarter  (*4)  in.  cotter. 

(c)  Connecting   pins   for   cranks,    compensators,   machine 
tail  levers,  bolt  locks,  switches,  pipe  connected  levers,  etc., 
shall  be  seven-eighths  by  two  and  three-eighths  (%x2%)  in. 
under  head  drilled  for  three-sixteenth  (3/16)  in.  cotter  and 
two  and  one-eighth   (2%)   in.  from  under  side  of  head,  and 
heads  of  all  connecting  pins  shall  be  either  square  or  hexagon. 

51.  Bolts,  Screws  and  Washers. 

(a)  All  bolts,  tap  bolts,  set  screws,  and  machine  screws 
shall  have  United  States  standard  screw  threads,  nuts  and 
heads. 

(b)  All  nuts,  bolt  heads,  tap  bolts  and  set  screws  in  con- 
nection with  the  machine  shall  have  hexagon  heads,  and  all 
other  nuts,  bolt  heads,  tap  bolts,  set  screws,  etc.,  shall  have 
square  heads. 

(c)  All  lag  screws  shall  be  standard  with  gimlet  points 
and  square  heads.     They  shall  be  screwed  their  entire  length 
in  holes  previously  filled  with  oil,  and  holes  shall  be  bored 
small  enough  to  provide  full  thread. 

(d)  Flat  cut  washers  shall  be  used  under  bolt  heads,  nuts 
and  heads  of  lag  screws  where  they  come  in  contact  with 
wood. 

52.  Shore  Foundations. 

(a)     Pipe    carrier   foundation    shall    consist    of    cast   iron 


380  APPENDIX. 

piers,  and  wood  or  iron  tops  and  bottoms  as  specified,  or  of 
concrete. 

(b)  Cast  iron  pipe  carrier  foundation  piers  shall  be  two 
(2)  ft.  five  and  one-half  (5%)  in.  long,  cored  at  top  for  two 

(2)  one-half   (M»)   in.  bolts,  spaced  five  and  one-half   (5%) 
in.  between  centers,  cored  at  bottom  for  one   (1)    one-half 
(%)  in.  bolt  one  and  one-quarter  (l^)  in.  from  center  line, 
and  the  average  weight  of  piers  shall  be  not  less  than  twen- 
ty-two  (22)   Ibs. 

(c)  Wood  pipe  carrier  foundation  tops  and  bottoms  shall 
be  made  of  two  and  three-quarter  by  seven  and  three-quarter 
(2%x7%)  in.  yellow  pine  lumber,  dressed  four  (4)  sides. 

(d)  Foundation  for  one  (1)  one  (1)  way  pipe  carrier  in 
main  pipe  line  shall  be   seventeen  and  one-half   (17%)    in. 
long  and  two  and  three-quarters  (2%)  in.  shall  be  added  for 
each  additional  pipe  carrier. 

(e)  Foundations  used  for  one  way  pipe  carriers  in  trans- 
verse pipe  lines  shall  be  twelve  (12)  in.  long. 

(f)  Pipe  carrier  foundation  tops  shall  be  bored  at  each 
end  for  two    (2)    one-half    (%)   in.  bolts   one  and  one-half 
(1^)  in.  from  end  to  center  and  five  and  one-half  (5%)  in. 
between  centers.     Pipe  carrier  foundation  bottoms  shall  be 
bored  at  each  end  for  one   (1)   one-half  (%)   in.  bolt  three 

(3)  in.   from   end  and  one   and  one-quarter   (1^4)   in.  from 
center  line. 

(g)  Two  (2)  cast  iron  piers  shall  be  used  for  each  pipe 
carrier  foundation  up   to   forty-five    (45)    in.   long,  and   one 
additional  pier  shall  be  provided  for  each  additional  thirty- 
six  (36)  in.  or  fraction  thereof,  and  intermediate  piers  shall 
be  inverted. 

(h)     Pipe   carrier  foundation  tops  and  bottoms  shall  be 
fastened  to  piers  with  one-half  by  four  (%x4)  in.  bolts. 
53.  Concrete  Foundations. 

(a)  Cranks,  compensators  and  bolt  locks  shall  be  fastened 
to  iron  piers  arranged  with  slot  for  three-quarter   (%)   in. 
bolts,  and  set  in  concrete.     Plank  to  hold  dwarf  signals,  de- 
flecting bars,  wheels,  etc.,  shall  be  four  by  twelve  (4x12)  in. 
yellow  pine,  dressed  two  (2)  sides,  and  fastened  in  a  similar 
manner. 

(b)  All  foundations  shall  be  so  constructed  that  apparatus 
can  be  removed  without  disturbing  the  foundations. 

(c)  Foundations  for  straight  signal  post  shall  consist  of 
four  (4)  one  (1)  in.  by  three  (3)  ft.  bolts  set  to  templet  in 
concrete. 

(d)  Foundation  for  bracket  signals  shall  consist  of  four 

(4)  one  and  one-half  in.  by ft.  (1%  in.  x 

ft.)  bolts  set  to  templet  in  concrete. 


APPENDIX.  381 

(e)  All    concrete    foundations    shall    be    set    parallel   to 
track. 

(f)  Dimensions  of  concrete  foundations  shall  be  as  fol- 
lows: 

Top.  Base.  Depth. 

Cranks     20x18  in.  36x34  in.  36  in. 

Compensators    34x18  in.  50x34  in.  36  in. 

Two  way  chain  wheels  . .  22x18  in.  38x34  in.  36  in. 

Dwarf    signal 30x16  in.  30x16  in.  36  in. 

Straight  post  signal 26x26  in.  36x36  in.  4  ft. 

Bracket  signal    38x38  in.  48x48  in.  5ft. 

(g)  Concrete  foundations  shall  stand  until  properly  set 
before  any  apparatus  is  connected  thereto. 

(h)  All  foundations  shall  be  rigid,  level,  and  in  perfect 
line. 

(i)  Wooden  stakes  for  wire  lines  shall  be  three  by  four 
inches  by  five  feet  (3  in.  by  4  in.  x  5  ft.)  with  seven  (7)  in. 
point. 

Note. — The  plans  and  specifications  for  concrete  founda- 
tions are  adaptable  to  solid  grounds.  The  Contractor  is 
expected  to  use  his  best  judgment  as  to  the  proper  size  and 
depth;  and  he  will  be  governed  by  nature  of  ground. 

54.  Concrete. 

(a)  Concrete  shall  be  made  of  one  part  Portland  cement, 
three  parts  sand,  six  parts  of  broken  stone  and  water  to 
make  proper  consistency. 

(b)  The  outer  exposed  face  to  a  thickness  of  one  (1)  in. 
shall  consist  of  one  part  of  Portland  cement,  one  and  one- 
half  (1%)  part  sand,  deposited  simultaneously  with  the  in- 
terior mass.     The  top  surface  shall  be  floated  and  rubbed 
smooth  by  hand  and  true  to  grade  and  line. 

55.  Painting. 

(a)  General. — All  material  shall  be  pure  and  the  quality 
of  paint  mixed  shall  be  such  as  will  permit  of  the  applica- 
tion herein  specified. 

(b)  Cleaning. — Surfaces  covered  with  rust,  grease,   dirt 
or  other  foreign  substances  shall  be  thoroughly  cleaned  be- 
fore paint  or  oil  is  applied. 

(c)  Application. — General.    Paint  shall  not  be  applied  to 
outside  surfaces  in  freezing  weather  or  to  wet  surfaces  until 
they  are  thoroughly  dried. 

(d)  Pigment  finishing   coats   shall  be  sufficient  body  to 
form  an  opaque  coating. 

(e)  Finishing  coats  shall  not  be  applied  until  after  the 
expiration  of  forty-eight  (48)  hours  after  the  previous  coat- 
ing has  been  applied. 


382  APPENDIX. 

(f)  All  priming  coats  shall  be  applied  as  soon  as  is  con- 
sistent with  the  progress  of  the  work. 

(g)  All  second  coats  shall  be  applied  in  sufficient  time 
for  the  third  coat  to  be  applied  and  dry  when  the  plant  is 
completed. 

(h)  All  iron  work,  except  machine,  tie  plates,  and  iron 
foundation  piers,  shall  be  painted  one  coat  of  red  lead  and 
raw  linseed  oil,  and  two  (2)  finishing  coats. 

(i)     The  following  specific  finishing  coats  shall  be  used: 

Kind  of  paint.          Color. 

Signal  bridges  and  brackets 

Signal    masts    

All  connections    

(j)  Machine. — The  machine  shall  be  painted  one  priming 
coat  and  one  finishing  coat  of  black  japan  from  top  of  latch 
shoes  to  foundation  supports. 

(k)  The  levers  shall  be  painted  one  priming  coat  and  two 
finishing  coats,  as  follows: 

Lock  levers,  blue. 

Switch  levers,  black. 

Switch  and  lock  levers,  black  and  blue.  Bottom  half  black 
and  top  half  blue. 

Distant  signal  levers,  lawn  green  or  lemon-yellow. 

Home   signal  levers,  vermillion. 

Spare  levers,  white. 

(1)  The  unfinished  part  of  latch  handle  shall  be  painted 
same  color  as  lever. 

(m)  All  painted  parts  of  machine  above  the  floor  shall 
have  one  coat  of  outside  finishing  varnish.  The  finished 
parts  of  the  machine  shall  not  be  painted.  All  machine  fin- 
ished metal  shall  be  slushed  in  white  lead  and  linseed  oil, 
except  locking,  which  shall  be  coated  with  vaseline  before 
being  shipped. 

(n)  All  chain  and  other  iron  work,  not  machine  finished, 
shall  be  dipped  in  oil  before  being  shipped. 

(o)  Wood  Work. — Exposed  wood  work  shall  be  given  one 
priming  coat  and  finishing  coats  as  follows: 

Kind  Number 

paint.         Color.  coats. 

Home  signal  blades 

Dwarf   signal   blades 

Distant    signal   blades 

Foundation    tops    and    bot- 
toms              

(o)  Building. — Signal  stations,  if  built  of  wood,  shall  re- 
ceive one  priming  coat  and  two  finishing  coats  as  specified 
below. 


APPENDIX.  383 

(q)  The  priming  coat  shall  consist  of  yellow  ochre,  and, 
when  thoroughly  dry,  two  coats  of  pure  lead  and  oil,  in  the 
following  tints: 


Prepared  paints  manufactured  by. 


will  be  accepted. 
56.     Boxing. 

Where  boxing  is  specified,  it  shall  be  made  of  two  by  eight 
(2x8)  in.  lumber,  dressed  on  one  side.     If  bottom  in  boxing 

is  specified,  it  shall  be  made  of  one  (1)  in rough 

lumber.  Where  boxing  is  required  through  highways,  the 
sides  shall  be  made  of  three  by  six  (3x6)  in.  and  three  by 

ten  (3x10)  in lumber  and  shall  be  spiked  to  the 

foundation  tops.  Four  by  twelve  (4x12)  in lum- 
ber shall  be  used  for  the  tops  and  it  shall  be  cut  diagonally, 
and  not  nailed  to  the  sides. 


384 


APPENDIX. 


III!!1 


3: 


asa 


,'a& 


Ills 


APPENDIX. 


385 


SPECIFICATIONS  FOE  POWER  INTERLOCKING.  x 
General. 

1.  Specifications.  5.     Permits. 

2.  Drawings.  6.     Accidents. 

3.  Supervision.  7.     Payments. 

4.  Alterations.  8.     Contract. 

Detail. 

10.  Intent. 

11.  Supplementary  Data. 
12     Material  and  Workman- 
ship. 

13.  Transportation. 

14.  Track  Work. 

Buildings. 

20.  Tower. 

21.  Power  House. 

22.  Foundations. 

Power  Plant. 

30.  Composition  and  Loca- 
tion. 

31.  Engine. 

32.  Generator. 

33.  Motor. 
Machine. 

40.  Capacity. 

41.  Locking. 

42.  Levers. 
Signals. 

50.  General. 

51.  Lanterns. 

52.  Arms  and  spectacles. 

Switches. 

60.  General. 

61.  Mechanical    c  o  n  n  e  c  - 
tions. 

62.  Detector  Bars  and  De- 
Wire  and  Wiring. 

70.  Specifications. 

71.  Size. 

72.  Tagging. 
Wire  Protection. 

80.  Trunking  and  Conduits. 

81.  Supports. 

82.  Junction  Boxes. 


15.  Obstacles. 

16.  Traffic. 

17.  Completion. 

18.  Provided  by  Purchaser. 

19.  Tenders. 


23.  Gasoline  Tank. 

24.  Lighting. 

25.  Appurtenances. 

34.  Motor  Generator. 

35.  Transformers. 

36.  Storage  Battery. 

37.  Switchboard. 


43.  Indication. 

44  Terminal  Board. 

45.  Case. 

53.  Foundations. 

54.  Electric   Lighting. 


tector  Track  Circuits. 
63.     Switch  Circuit  Control- 
lers. 


73.  Runs. 

74.  Common. 

75.  Joints. 

83.  Lightning  Arresters. 

84.  Fuses. 


386 


APPENDIX. 


Circuits. 

90.  General. 

91.  Signals. 

92.  Switches. 

93.  Cross  Protection. 
Track  Circuits, 

100.  General. 

101.  Bonding. 

102.  Insulated  Joints. 

103.  Track  Battery. 

104.  Battery  Housing. 
Painting. 

110.  General. 

111.  Cleaning. 

112.  Mixing. 
Special. 

Supplementary  Specifications 


94.  Switchboard. 

95.  Electric  Lighting. 

96.  Special. 


105.  Relays. 

106.  Relay  Housing. 

107.  Switch  Protection. 

108.  Connections. 


113.  Application. 

114.  Buildings. 


120. 

for  Drawbridge. 
130.     Locking. 


GENERAL. 

1.  Specifications. 

Adherence. — All  the  work  herein  outlined  is  to  be  done 
in  strict  accordance  with  the  specifications,  the  accompany- 
ing plans  and  such  instructions  as  may  be  given  from  time 
to  time  by  the  purchaser. 

Spirit. — The  nature  and  spirit  of  these  specifications  are 
to  provide  for  the  work  herein  enumerated  to  be  fully  com- 
pleted in  every  detail  for  the  purpose  designed;  and  it  is 
hereby  understood  that  the  contractor  in  accepting  the  con- 
tract agrees  to  furnish  any  and  everything  obviously  neces- 
sary for  such  construction. 

Special  Work. — The  purchaser  will  furnish  herewith  de- 
scription and  drawings  of  all  special  work. 

Copies. — Duplicate  copies  of  these  specifications  will  be 
furnished  by  the  purchaser  with  request  for  tender. 

2.  Drawings. 

Preliminary. — The  purchaser  will  furnish  with  each  copy 
of  the  specifications  copies  of  all  drawings  indicating  the 
work  to  be  performed. 

The  contractor  shall  examine  these  drawings,  call  the  pur- 
chaser's attention  to  any  apparent  errors  and  ascertain  the 
purchaser's  wishes  regarding  the  same  before  submitting  a 
tender. 

Final. — After  the  contract  has  been  awarded,  the  con- 
tractor shall  submit  three  (3)  sets  of  the  drawings  showing 


APPENDIX.  387 

proposed  arrangement  or  construction,  which  require  the  pur- 
chaser's approval,  one  set  of  which  will  be  approved  and 
promptly  returned.  Should  changes  in  these  drawings  be 
necessary  to  meet  the  requirements  of  the  spcifications,  one 
set  will  be  promptly  returned  with  such  changes  indicated  in 
writing,  and  the  contractor  may  proceed  with  the  work  when 
such  corrections  have  been  made. 

The  contractor  shall  furnish  four  (4)  sets  of  working 
drawings  for  the  purchaser's  files  and  upon  request  two  (2) 
additional  sets  for  the  file  of  each  other  interested  company. 

Suitable  framed  manipulation  chart  and  track  diagram 
shall  be  furnished  in  place  by  the  

3.  Supervision. 

Supervision. — All  work  shall  be  under  the  supervision  of 
the  purchaser's  accredited  representative  hereinafter  re- 
ferred to  as  the  supervisor. 

*Foreman. — The  foreman  of  installation,  and  his  men,  shall 
be  satisfactory  to  the  supervisor. 

Instructions. — The  foreman  of  installation  shall  receive 
and  act  upon  all  instructions  given  by  the  supervisor  in  writ- 
ing, which  do  not  involve  additional  expense  to  the  con- 
tractor. 

Inspection. — All  materials  and  workmanship  will  be  in- 
spected thoroughly  and  carefully,  and  the  contractor  will  be 
held  at  all  times  to  the  spirit  of  the  specifications. 

The  supervisor  shall  be  given  free  access  to  all  parts  of 
the  work  during  the  process  of  construction. 

The  purchaser  will  make  a  final  inspection  and  tests  with- 
in three  (3)  days  after  the  completion  of  the  work.  Any 
defects  or  omissions  noted  during  this  inspection  shall  be 
made  good  by  the  contractor  without  extra  charge  before 
the  work  will  be  accepted  and  paid  for  in  full. 

Defective  work. — The  contractor,  upon  being  so  directed 
by  the  purchaser,  shall  remove,  rebuild  or  make  good,  with- 
out charge,  any  defective  work. 

4.  Alterations. 

Specifications. — The  purchaser  reserves  the  right  to  make 
changes  in  plans  and  specifications.  All  such  changes  shall 
be  handled  in  the  same  manner  as  the  originals. 

Extras. — Alterations  involving  an  increase  in  cost  of  the 
amount  of  material  to  be  furnished,  or  an  increase  in  cost  of 
work  to  be  performed,  shall  be  classed  as  extras. 

Credits. — Alterations  involving  a  decrease  in  cost  of  the 
amount  of  material  to  be  furnished,  or  a  decrease  in  cost  of 
work  to  be  performed,  shall  be  classed  as  credits. 

Compensation. — No  compensation  shall  be  allowed  for  ex- 
tras or  credits  unless  agreed  to  in  writing. 


388  APPENDIX. 

5.  Permits. 

The  purchaser  will  furnish  all  necessary  permits.  Work 
requiring  permits  shall  not  be  performed  until  same  have 
been  provided. 

6.  Accidents. 

Precaution. — The  contractor  shall  place  sufficient  and 
proper  guards  for  the  prevention  of  accidents  and  shall  put 
up  and  maintain  at  night  suitable  and  sufficient  lights,  except 
as  specified  in  Article  16. 

Responsibility. — The  contractor  shall  save  the  purchaser 
harmless  and  relieve  him  from  all  responsibility  for  any  dam- 
age, injury  or  loss  suffered  by  any  person  or  persons  in  the 
employ  of  the  contractor  while  such  person  or  persons  are 
engaged  in  the  construction  of  interlocking,  unless  such  dam- 
age, injury  or  loss  is  caused  by  the  negligence  of  the  pur- 
chaser. 

7.  Payments. 

First  Payment. — The  purchaser  will  pay 

per  cent  of  the  contract  price  upon  receipt  of  the  material  on 
the  site  of  the  work. 

Second  Payment. — The  plan  will  be  accepted  and  remain- 
ing   per  cent  of  the  contract  price  will  be  paid 

within  thirty  (30)  days  after  completion  in  conformity  with 
the  plans  and  specifications. 

Extras. — Payments  of  extras  involving  additional  com- 
pensation will  be  made  in  the  same  manner  as  prescribed  for 
the  contract  price. 

Credits  involving  a  reduction  in  compensation  will  be  re- 
duced from  the  contract  price. 

8.  Contract. 

As  soon  as  possible  after  the  award  is  made,  the  contract, 
in  accordance  with  the  accompanying  form,  will  be  presented 
in  duplicate  to  the  contractor  for  his  signature,  after  which 
both  copies -will  be  signed  by  the  purchaser  and  one  of  them 
will  be  returned  to  the  said  contractor. 
DETAIL. 

10.  Intent. 

The  intent  of  this  specification  is  to  clearly  describe  all  of 
the  material  and  labor  required  for  and  the  results  to  be  ob- 
tained by  the  complete  installation  of  an  electrically  operated 

interlocking  plant  at on  the  lines  of  the 

E.  E.,  as  shown  in  the  plans  and  supple- 
mentary data  hereto  attached. 

Eesults. — Note. — This  space  is  provided  for  a  complete 
general  description  of  the  plant  and  all  its  adjuncts  and  of 
the  operating  results  to  be  obtained  therefrom. 

11.  Supplementary  Data. 


APPENDIX.  389 

Practice. — The  contractor's  recognized  best  practice  shall 
govern,  except  as  herein  otherwise  provided. 

The  plans,  drawings  and  detail  specifications  attached  to 
and  forming  a  part  of  these  specifications  are: 


12.  Material  and  Workmanship. 

When  it  is  necessary  or  desirable  to  use  apparatus  not 
heretofore  in  use,  the  contractor  shall  submit  drawings  of 
the  same  with  his  proposal  and  the  acceptance  of  such  pro- 
posal shall  constitute  acceptance  of  such  new  devices. 

All  material  and  workmanship  shall  be  first-class  in  every 
respect. 

The  contractor  shall  furnish  for  replacement,  free  of  cost, 
f.  o.  b.  works,  any  apparatus  or  material  of  his  own  manu- 
facture, or  furnished  on  his  specification  which,  when  used 
for  its  intended  purpose,  shall  prove  defective  within  a  period 
of  one  year  after  having  been  placed  in  service.  Defective 
material  will  be  returned  upon  written  request  and  at  the 
expense  of  the  contractor. 

The  contractor's  standard  apparatus  shall  be  used,  except 
as  herein  otherwise  specified. 

Electric  apparatus  shall  withstand  an  insulation  test  at  the 
works  of  three  thousand  (3,000)  volts  A.  C.  applied  for  one 
minute. 

All  magnets  and  solenoids  shall  be  plainly  marked  with 
their  resistance  and  the  size  of  wire  with  which  they  are 
wound. 

Field  coils  of  motors  and  all  other  magnet  windings  of 
mechanism  shall  be  securely  held  to  prevent  vibration. 

Note. — It  is  recommended  that  all  windings  for  apparatus 
for  electric  interlocking  shall  be  treated  by  a  thorough  im- 
pregnation process  to  resist  moisture  and  improve  the  insula- 
tion. 

13.  Transportation. 

The  purchaser  will furnish  transportation  for 

the  men  engaged  in,  and  necessary  tools  and  material  re- 
quired for,  the  installation  of  the  plant  over  the  following 
railway  lines: 


390  APPENDIX. 

Shipment  and  Handing. — Tools  and  material  are  to  be 
shipped 

To    

Care  of 

At 

Via    

Marked     

Freight  prepaid  to 

The  purchaser  will  unload  and  properly  house  only  such 
material  as  arrives  in  advance  of  the  contractor's  men. 

The  use  of  the  following  cars  will  be  permitted  under  the 
restrictions  of  Articles  Nos.  6  and  16,  unless  otherwise  in- 
dicated in  this  paragraph: 

Number.     Furnished  by 

Motor  cars 

Velocipede  cars   

Handcars   

Pushcars 

When  the  contractor  is  not  permitted  to  use  handcars  or 
pushcars,  the  purchaser  will,  at  his  own  expense,  distribute 
all  material  to  the  point  of  use  upon  receipt  of  notification 
from  and  under  supervision  of  contractor's  foreman. 

The  contractor  shall  call  upon  the  purchaser  for  the  re- 
quired number  of  cars  for  the  return  of  tools  and  unused 
material,  and  same  will  be  furnished  in  ....  days,  after 
which  time  the  purchaser  will,  at  its  own  expense,  care  for 
and  load  all  tools  and  material. 

14.  Track  Work. 

The  purchaser  will  furnish: 

All  switches,  derails  and  movable  point  frogs  in  place  ad- 
justed to  the  required  throw. 

All  ties  in  place  required  for  the  support  of  the  apparatus. 

All  rail  braces  and  will  install  all  except  those  located  on 
the  plates  furnished  by  the  contractor. 

All  insulated  rail  joints  in  place. 

The  purchaser  will  move  all  ties  which  interfere  with  in- 
stallation of  the  interlocking  apparatus  or  connections. 

The  purchaser  will  remove  all  guard  rail  clamps,  rail 
braces,  anti-creepers  and  lips  and  otherwise  prepare  the  rail 
for  installation  of  detector  bars. 

The  purchaser  will  remove  and  replace  all  switch  and  tie 
rods  (other  than  front  rods  on  interlocked  switches)  requir- 
ing a  change  in  location,  the  application  of  insulation,  adjust- 
ment brackets  or  other  alterations. 

15.  Obstacles. 

The  purchaser  will  do  all  preliminary  grading,  provide  ade- 
quate drainage  and  blast  and  remove  all  solid  rock  that  will 


APPENDIX.  891 

interfere  with  the  placing  of  the  interlocking  apparatus  or 
connections. 

The  purchaser  will  furnish  all  extra  labor  and  material  re- 
quired to  place  apparatus  or  connections  in  or  under  all  plat- 
forms, roadways  or  walks,  the  location  and  construction  of 
which  are  not  herein  specified. 

16.  Traffic. 

The  contractor  shall  not  unnecessarily  delay  or  interfere 
with  traffic.  When  it  becomes  necessary  for  contractor  to 
perform  any  work  which  may  interfere  with  or  endanger 
traffic,  the  contractor  shall  notify  the  purchaser  and  shall 
not  proceed  with  said  work  until  traffic  is  protected. 

The  purchaser  will  promptly  arrange  to  protect  traffic  upon 
request  of  contractor. 

17.  Completion. 

The  contractor  shall  notify  the  purchaser,  in  writing,  not 
less  than  seven  (7)  days  before  the  plant  will  be  ready  for 
service. 

The  contractor  shall  put  the  plant  in  service  under  the 

supervision  of  the  purchaser,  and  shall  leave  

competent  men  on  duty  for hours  thereafter. 

The  purchaser  will  maintain  and  operate  the  plant  as  soon 
as  it  is  put  in  service. 

The  purchaser  will  put  the  plant  in  service,  providing  this 
cannot  be  done  within  three  (3)  days  after  the  completion  of 
the  contractor's  work. 

The  contractor  shall  remove  and  dispose  of  all  excess  earth 
and  all  refuse  made  by  the  contractor's  men  or  shall  load  on 
cars,  where  disposal  cannot  be  made  on  right-of-way  within 
interlocking  limits. 

18.  Provided  by  Purchaser. 

a    

b    

c    

d    

e    

Note. — Items  to  be  provided  by  purchaser  should  be  assem- 
bled and  filled  in  at  this  point. 

19.  Tenders. 

Sealed  tenders  for  the  work  covered  by  these  specifications 
will  be  received: 

by  

at , 

up  to hour  of  the day  of month 

of    at   which   time   and  place   said  tenders   will  be 

opened.    Bidders  are  invited  to  be  present. 
Tenders  shall  be  divided  as  follows: 


392 


APPENDIX. 


Note. — This  space  is  provided  for  a  complete  description 
of  the  manner  in  which  the  tenders  are  to  be  divided  for  the 
different  portions  of  the  work. 


b    

c     

d    •• 

The  purchaser  reserves  the  right  to  reject  any  and  all  bids. 

20.  Tower. 

A  building  for  tower stories  high,  and 

x ,  inside  dimensions,  shall  be  built  by  the 

in  accordance  with  specifications  and  drawings 

for  building  and  drawings for  frame. 

Note. — In  erecting  a  wooden  tower  provision  should  be 

made  for  leadout  wires  in  an  asbestos  lined  or lined 

chase,  accessible  for  its  entire  length.  Not  less  than  fifty 
(50)  per  cent  of  the  capacity  of  the  chase  will  remain  free 
for  the  further  installation  of  wires. 

When  fireproof  towers  are  erected  a  special  chase  for  en- 
trance of  wires  should  be  provided. 

21.  Power  House. 

A building  for  power  house stories  high 

and x ,  inside  dimensions,  shall  be  built  by 

the in  accordance  with  specifications  and  drawings 

for  building  and  drawings for  frame. 

22.  Foundations. 

foundations  for  the  buildings  shall  be  built  by 

the  in  accordance  with  specifications  and  draw- 
ings   

23.  Gasoline  Tanks. 

Housing  for  gasoline  tank  as  per  drawing ,  lo- 
cated not  more  than  ft.  from  the  power  house, 

will  be  built  by 

24.  Lighting. 

The  number,  kind,  size  and  distribution  of  electric  lamps 
shall  be  as  follows: 


Boom. 

Number. 

Candle- 
power. 

Location  and 
Description. 

Operating  Eoom 

Lower  Story 

Battery  Eoom 

Generator  Eoom 

Special 

APPENDIX.  393 

Lights  shall  be  controlled  by  switches  located  as  follows: 
Number. 

Operating  Eoom  Lamps 

Lower  Story  Lamps 

Battery  Eoom  Lamps 

Generator  Eoom  Lamps 

Special  Lamps 

Fixtures  for  electric  lamps  will be  required.    When 

required  they  will  be  provided  by  purchaser  and  installed  by 
contractor. 

The  electric  lights  and  accessories  shall  be  acceptable  to 
and  installed  under  the  rules  of  the  National  Board  of  Fire 
Underwriters  and  the  attached  requirements  of  the  local  au- 
thorities. 
25.  Appurtenances. 

Except  as  otherwise  specified,  all  tools,  fixtures  for  build- 
ings, and  supplies  required  for  the  operation  of  the  plant  will 
be  furnished  by  purchaser. 

POWEE  PLANT. 

30.  Composition  and  Location. 

The  power  plant  shall  consist  of: 

engine   connected  to 

motor    connected  to 

generator   

transformer,  together  with 

mercury  arc  rectifier charging  rheostat 

operating  switchboard 

motor   starting   panel and    

storage  batteries,  each  composed  of cells,  all  in 

accordance  with  detailed  specifications  herein  and  shall  be  in- 
stalled by  the in  the  locations  provided  by 

the 

31.  Engine. 

A cylinder cycle 

Vertical          ) 

Horizontal      )    engine  of brake  H.  P. 

Turbine  ) 

manufactured  by installed  by  the 

shall  be  furnished  on  a foundation  to  be  fur- 
nished in  place  by  the built  in  accordance  with 

the  standard  specifications  of  the and  plans  of 

the  manufacturer  of  the  engine  dated. . '. 

A  complete  set  of  wrenches  shall  be  furnished. 

Note. — This  space  is  provided  for  detailed  specifications  of 
engine  to  be  used. 


394  APPENDIX. 

(a)  

(b) 

(c)  

(d) 

(e) 

Note. — The  engine  should  be  of  such  type  as  to  be  easily 
accessible  for  attention  to  bearings,  adjusting  and  cleaning. 

Note. — For  power  interlocking  work,  as  a  simple  and  de- 
sirable method  of  operation,  a  constant  rate  of  charging  for 
the  storage  battery  is  taken  as  the  basis  for  the  establish- 
ment of  the  recommended  capacity  ratios  between  the  bat- 
tery, the  generator  and  the  engine. 

GASOLINE  ENGINE  SPECIFICATIONS. 

The  recommended  brake  horse  power  of  the  gasoline  en- 
gine shall  be  not  less  than  one  and  three-quarters  times  the 
kilowatt  capacity  of  the  generator  at  the  maximum  voltage 
and  the  eight  hour  charging  rate. 

The  engine  shall  run  without  injurious  vibration  and  shall 
operate  continuously  at  manufacturer's  specified  capacity  for 
a  period  of  sixteen  (16)  hours  without  injurious  heating  in 
any  part. 

Kegulation  in  speed  shall  be  within  three  (3)  per  cent  from 
no  load  to  full  load  and  the  regulation  as  recorded  on  the 
voltmeter  for  a  given  current  shall  not  vary  more  than  two 
(2)  per  cent  between  impulses. 

Electrodes  on  the  engine  for  electric  ignition  shall  be 
tipped  with  platinum  or  an  equally  serviceable  material. 

The  manufacturer's  standard  exhaust  muffler  shall  be  pro- 
vided. 

The  engine  and  accessories  shall  be  acceptable  to  and  in- 
stalled under  the  rules  of  the  National  Board  of  Fire  Under- 
writers and  the  attached  requirements  of  the  local  author- 
ities. 

Engines  of  twenty-five  (25)  H.  P.  or  less  shall  not  exceed 
a  speed  of  four  hundred  revolutions  per  minute. 

A  gasoline  tank  of gallons  capacity  shall  be 

furnished.  Both  fuel  and  cooling  tanks  shall  be  made  of 
iron  or  steel  with  brazed  or  riveted  seams.  All  tanks  shall 
be  dipped  in  the  galvanizing  kettle  after  they  are  put  to- 
gether. 

Sufficient  piping  shall  be  furnished  to  locate  the  gasoline 
tank ft.  from  the  engine. 

Unions  in  all  piping  shall  be  equipped  with  ground  brass 
seats. 

Note. — For  tanks  both  for  fuel  and  water  it  is  recom- 
mended that  selection  shall  be  made,  when  practicable,  from 
the  following  table: 


APPENDIX.  895 

GASOLINE   TANKS  FOE  EAILEOAD  WOEK. 


Capacity. 
Gallons 

Inches  in 
Diameter. 

Inches  in 
Length. 

Gage  of  Metal. 

Head. 

Body. 

66 
120 

500 

18 
24 
36 

68 
66 
120 

No.  14 
No.  12 
No.  10 

No.  16 
No.  14 
No.  12 

As  a  guide  in  ordering  tanks  it  is  good  practice  to  consider 
that  it  will  require  one-tenth  (1/10)  of  a  gallon  of  gasoline 
per  H.  P.  hour  for  gasoline  engines. 

For  cooling  the  minimum  of  free  running  water  should  not 
be  less  than  ten  (10)  gallons  per  H.  P.  hour  and  for  the 
circulation  tank  system  not  less  than  fifty  (50)  gallons  per 
H.  P. 

Unless  otherwise  specified,  an  iron  or  a  steel  cooling  tank 
of  sufficient  capacity  for  a  continuous  run  of  ten  hours  on 
one  filling,  with  connections  and  removable  cover,  shall  be 
furnished.  Connections  between  engine  and  tank  shall  be 
arranged  for  convenient  and  complete  drainage  of  the  cooling 
system,  for  independent  drainage  of  the  engine  and  tank,  and 
to  conduct  all  waste  water  and  steam  to  the  outside  of  the 
building. 
32.  Generator. 

The  generator  shall  be  shunt  wound,  self-excited,  shall 
have  self -oiling  bearings,  carbon  brushes,  rheostat,  and  when 
belt  connected,  a  belt  tightener,  sub-base  and  pulley. 

The  normal  or  rated  speed  shall  not  exceed  1,500  E.  P.  M., 
except  when  direct  connected  to  an  A.  C.  motor  or  steam 
turbine. 

The   generator   shall   have   a   continuous  current   capacity 

equal  to  the  eight  hour  rate  ( Amp.)  of  the  battery,  at 

a  voltage  equal  to  the  maximum  voltage  ( .  . . .  volts)  of  the 
battery  on  charge,  without  a  rise  in  temperature  in  any  part 
exceeding  40  degrees  C.  (72  degrees  F.),  above  the  tempera- 
ture of  the  surrounding  atmosphere.  It  shall  be  so  wound 
that  its  voltage  at  the  continuous  current  rating  given  above 
may  be  varied  by  means  of  a  field  rheostat  from  the  mini- 
mum to  the  maximum  charging  voltage  of  the  battery.  The 
generator  shall  be  capable  of  supplying  for  four  hours  a  cur- 
rent output  twenty-five  (25)  per  cent  in  excess  of  the  con- 
tinuous current  capacity  referred  to  above  without  a  rise  in 
temperature  in  any  part  exceeding  50  degrees  C.  (90  degrees 
F.)  above  the  temperature  of  the  surrounding  atmosphere. 


396  APPENDIX. 

It  is  understood  that  the  temperature  of  the  surrounding 
atmosphere  is  to  be  based  on  25  degrees  C.  (77  degrees  F.), 
but  should  the  temperature  vary  from  this,  corrections  shall 
be  made  in  accordance  with  the  recommendations  of  the 
American  Institute  of  Electrical  Engineers. 

The  current  output  of  the  minimum  allowable  generator 
shall  be  that  required  for  the  operation  of  two  switches 
simultaneously. 

With  the  brushes  in  a  fixed  position,  the  generator  shall 
be  practically  sparkless  under  all  operating  conditions  as 
outlined  above. 

Note. — These  generator  specifications  will  fix  a  machine 
which  in  normal  power  interlocking  service  will  have  an 
ample  overload  capacity  to  meet  general  requirements. 

33.  Motor. 

The  motor  shall  be H.  P.,  with  a  rated  speed  not 

to  exceed  1,500  E.  P.  M.,  if  direct  current,  or  1,800  E.  P.  M., 
if  alternating  current,  and  shall  have  automatic  regulation 

to  within  20  per  cent  when  operating  on to 

volts,  D.  C.,  or  on to volts cycles, 

phase  A.  C.,  shall  conform  to  generator  specifica- 
tions regarding  heating,  sparking  and  insulation,  and  shall 
be  furnished  with  a  starting  panel. 

34.  Motor  Generator. 

Motor  generators  shall  be  direct  connected,  mounted  on  a 
cast  iron  sub-base  and  shall  conform  to  the  specifications  for 
motors  and  generators. 

35.  Transformers. 

36.  Storage  Battery. 

(1)  The   storage  battery   shall   consist   of cells 

A.  H.  capacity type  at  eight  hour  rate 

with  glass  jars  manufactured  by or 

(2)  The  storage  battery  shall  consist  of cells 

manufactured  by of  sufficient  capacity  to 

operate  the  interlocking  plant,  together  with  all  accessories 
which  obtain  a  current  supply  from  the  main  battery,  electric 

lighting included,  for  a  period  of days 

on  one  charge,  on  the  basis  of lever  movements 

and  of  lights  burning hours  per  twenty-four  hours. 

Batteries  up  to  four  hundred  A.  H.  capacity  shall  be  placed 
in  glass  jars.  All  batteries  shall  be  rated  for  an  eight  (8) 
hour  discharge  at  70  degrees  F. 

Note. — For  a  battery  of  a  capacity  greater  than  four  hun- 
dred A.  H.,  wooden  tanks  should  be  required  and  should  be 
covered  by  special  specifications. 

Note. — It  should  be  borne  in  mind  both  that  the  capacity 
of  a  storage  cell  decreases  with  a  decrease  in  temperature 
and  that  the  extent  of  such  decrease  should  be  obtained  from 


APPENDIX.  397 

the  manufacturer,  and  also  that  the  number  of  days  of  excess 
capacity  for  the  battery  to  be  allowed  should  be  stated  and 
depends  upon  conditions  of  maintenance  and  operation,  for 
example,  frequency  of  visits  of  maintainer. 

The  cells  shall  be  connected  by  lead  covered  bolts.  Burnt 
connections  shall  be  used  when  specified.  The  rows  of  cells 
shall  be  connected  together  by  lead  strips  of  as  great  a  sec- 
tional area  as  the  connections  between  cells,  or  by  lead 
coated  copper  connections  of  equivalent  carrying  capacity. 
Such  connections  shall  be  considered  a  part  of  the  battery. 

A  plan  showing  separate  battery  room  shall  be  furnished 
the  contractor. 

The  battery  shall  be  installed  with  a  minimum  vertical 
clearance  of  thirty  inches  above  the  jars  and  so  as  to  permit 
the  removal  of  any  element  without  disturbing  its  containing 
jar  or  adjacent  cells.  Unless  otherwise  specified,  the  battery 
shall  be  easily  accessible  from  both  sides  for  inspection  and 
attention.  Plates  shall  be  arranged  transversely  with  the 
rows. 

The  battery  shall  be  provided  with sand  trays 

which  shall  be  so  constructed  as  to  prevent  the  leakage  of 
sand  to  the  lower  cells. 

The  insulators  supporting  the  sand  trays  shall  rest  on 
wooden  racks  treated  with  an  acid-proof  paint. 

The  racks  shall  be  supplied  in  place  by  the in 

accordance  with  the  standard  plans  of  the ,  

hydrometers  and extra  jars  shall  be  provided. 

The  initial  charge  of  the  battery  shall  be  conducted  by 


The  instructions  of  the  manufacturer  shall  be  followed 
during  this  initial  charge  and  a  copy  of  the  readings  which 
are  taken  during  the  charging  period  shall  be  sent  to  him. 

The shall  provide  current  at  the  proper 

voltage  for  the  initial  charge. 
37.  Switchboards. 

General. — Switchboards  shall  be  made  of  oil-finished  slate 
not  less  than  one  (1)  in.  thick  and  free  from  metallic  veins 
or  flaws. 

They  shall  be  of  ample  size  to  accommodate  all  the  instru- 
ments, switches,  etc.,  required  for  the  operation  of  the  plant. 

They  shall  be  supported  on  substantial  iron  frames  and 
mounted,  when  not  more  than  twelve  (12)  in.  wide,  not  less 
than  fifteen  (15)  in.  from  the  wall. 

Note. — The  distance  between  a  switchboard  and  the  wall 
depends  on  the  width  of  the  board  and  the  voltage  employed. 

They  shall  be  acceptable  to  and  installed  under  the  rules 
of  the  National  Board  of  Fire  Underwriters  and  the  at- 
tached requirements  of  the  local  authorities. 


398  APPENDIX. 

The  finish  of  all  fittings  on  each  switchboard  shall  be  uni- 
form where  practicable. 

All  switches  shall  be  substantially  constructed  and  so 
mounted  as  to  preserve  their  alignment. 

Each  switch  shall  be  provided  with  a  plate  designating  the 
circuit  which  it  controls. 

National  Standard  enclosed  clip  fuses  of  the  required  ca- 
pacity shall  be  provided  for  all  circuits  not  otherwise  pro- 
tected. 

Power  Board. — The  power  board  shall  be  equipped  with 

one ammeter  and  one voltmeter,  ammeter 

to  be  arranged  to  show  current  in  any  circuit.  The  use  of 
external  multiple  shunts  will  not  be  permitted. 

Where  duplicate  charging  sets  are  used  a  voltmeter  switch 
shall  be  provided  for  connecting  meter  to  either  generator. 

A  no-load  reverse-current  circuit-breaker  shall  be  provided 
in  the  battery  charging  circuit. 

The  generator  field  rheostat  shall  be  mounted  on   

of  board. 

Motor  Starting  Panel. — Starting  box  for  D.  C.  motors 
shall  be  designed  to  protect  the  motor  from  overload,  both 
in  starting  and  running  positions,  and  in  case  of  failure  of 
the  line  voltage  or  opening  of  the  field  circuit  shall  return 
automatically  to  the  "off"  position. 

The  resistance  shall  be  proportioned  to  start  the  motor 
without  excessive  rushes  of  current  and  without  overheating. 

The  manufacturer's  standard  device  shall  be  furnished  for 
starting  A.  C.  motors. 

Operating  Board. — The  operating  board  shall  be  equipped 

with  a ammeter,  arranged  to  show  current  in  the 

operating  and  also  in  auxiliary  circuits  when  used.  The  use 
of  external  multiple  shunts  will  not  be  permitted.  When  low 
voltage  auxiliary  circuits  are  used,  the  ammeter  shall  be  pro- 
vided with  high  and  low  reading  scales. 

The  operating  board  shall  be  provided  with  one  2  candle 
power  lamp  for  detecting  grounds,  and  one  2  candle  power 
lamp  for  illuminating  ammeter  scale. 

Binding  posts,  with  two  nuts  and  two  washers  each,  shall 
be  provided  on  bottom  of  operating  board,  for  all  external 
connections. 

(D.  P.) 

The  operating  board   shall  be  provided  with  one 

(S.  P.) 

knife  switch  and the  National  Standard  en- 
closed fuses  for  the  control  of  each  signal  lighting  circuit 
where  same  are  required. 


APPENDIX.  399 

MACHINE. 

40.  Capacity. 

The  interlocking  machine  shall  have: 

levers  for one-arm  high  signals. 

levers  for two-arm    high    signals. 

levers  for arm  high  signal. 

levers  for one-arm    dwarf    signal. 

levers  for two-arm    dwarf    signal. 

levers  for switches  and  derails. 

levers  for movable  point  frogs. 

levers  for crossing  bars. 

levers  for lock  levers. 

levers  for spare  spaces. 

spare  spaces. 

Total  spaces. 

41.  Locking. 

The  machine  shall  be  provided  with  mechanical  locking  of 
the  preliminary  type,  so  designed  as  to  prevent  the  manipula- 
tion of  levers  for  conflicting  routes. 

Space  for  one  locking  bar  the  full  lentgh  of  the  machine 
shall  be  provided  in  the  locking  bed  for  each  spare  space  or 
spare  lever.  Locking  shall  be  so  arranged  as  to  be  easily 
accessible. 

42.  Levers. 

Levers  shall  be  numbered  to  correspond  with  attached 
plans.  Normal  and  reverse  latches  shall  be  provided. 

Lever  handles  shall  be  of  purchaser's  standard  color  as  per 
following  table: 

Home  signal  levers,  vermilion. 

Distant  signal  levers,  lawn  green  or  lemon  yellow. 

Lock  levers,  blue. 

All  other  levers,  black. 

43.  Indication. 

Each  lever  shall  be  provided  with  a  device  to  insure  cor- 
respondence in  the  movement  of  the  lever  and  that  of  the 
unit  controlled  thereby  before  the  release  of  the  mechanical 
locking  can  be  effected. 

Levers  shall  be  free  to  move  between  their  indicating 
positions. 

44.  Terminal  Board. 

The  machine  shall  be  provided  with  a  slate  terminal  board, 
having  binding  posts  for  making  all  connections  leading 
from  the  machine,  and  fuses  for  the  protection  of  the  circuit 
for  each  operated  unit. 

45.  Case. 

The  machine  shall  be  enclosed  in  a  case  to  prevent  im- 
proper manipulation. 
50.  General. 


400  APPENDIX. 

All  signals  shall  be  of  the  iron  pole  and  semaphore  type 
with  mechanism  enclosed  in  iron  case. 

Signals  shall  conform  as  to  location  and  dimensions  to  the 
Eailway  Signal  Association  standards. 

All  motors  in  place  shall  be  of  sufficient  capacity  and 
mechanism  constructed  to  perform  complete  operation  of  a 
ninety  (90)  degree  signal  of  Eailway  Signal  Association 

standard,  when  not  more  than ft.  from  interlocking 

machine,  in  not  more  than seconds  with  battery  at 

ten  (10)  per  cent  below  normal  voltage. 

The  normal  voltage  of  battery  is  one  hundred  and  ten 
(110). 

Note. — It  is  recommended  that  fair  working  conditions 
consist  of  a  distance  of  thirty-five  hundred  (3500)  ft.  from 
interlocking  machine  and  seven  (7)  seconds  of  time  of  com- 
plete operation. 

51.  Lanterns. 

(  oil          ) 

The  purchaser's  standard  (  )  lanterns,  as  man- 

(    convertible    ) 
ufactured  by shall  be  furnished  by 

52.  Arms  and  Spectacles. 

High  signal  arms  shall  be ft.  long,   in. 

wide  at  outer  end,  and  made  of  well  seasoned  clear  white  ash, 
or  equally  good  material. 

Dwarf  signal  arms  shall  be  flexible  or  hinged,  and 

in.  long. 

Painting  of  blades  shall  be  as  shown  on  Drawing  No , 

dated ,  attached. 

The  purchaser's  standard  signal  spectacle  castings  shall  be 

used,  as  shown  on  Drawing  No ,  dated , 

attached. 

Roundels  shall  be  solid  color,  one-fourth  (*4)  in.  thick, 
and  supplied  as  follows: 

Caution,  color   Dia .in. 

Dia in. 

Dia in. 

Dia in. 

Dia...  ..in. 


Stop,  color 
Proceed,  color 
Dwarf,  color 
Back,  color  . . 

Color  density  of  roundels  shall  be  as  per  attached  specifica- 
tions of  the  purchaser,  or  shall  be  within  the  following  limits: 

Scale. 

Color   Scale Scale. 

Bed to to 

Green to to 

Yellow to to 

Blue  to to 

Purple   to to 

53.    Foundations. 


APPENDIX.  401 

Foundations  shall  be  made  of  concrete,  and  in  general  con- 
form to  the  purchaser's  standard,  as  shown  on plan 

No ,  dated ,  attached. 

Dimensions  of  top  of  signal  foundations  shall  be  six  (6)  in. 
greater  than  dimensions  of  bottom  of  mechanism  case  or 
base  of  signal. 

The  minimum  foundation  shall  have  a  top  surface  two  and 
one-half  (2%)  ft.  square,  a  bottom  surface  three  and  one- 
half  (3%)  ft.  square,  with  a  vertical  height  of  four  (4)  ft. 

Concrete  shall  be  mixed  in  the  following  proportions: 


Anchor  bolts  for  high  signals  shall  be  one  (1)  in.  in  diam- 
eter and  three  (3)  ft.  long. 

Anchor  bolts  for  signal  brackets  shall  be  one  and  one-quar- 
ter (1*4)  in.  iQ  diameter  and  four  (4)  ft.  long. 

Ladders  shall  be  provided  with  foundations,  as 

shown  on  Drawing  No. ,  dated  attached. 

54.  Electric  Lighting. 

Electric  lighting  of  signals  will   be  required. 

Convertible  lanterns  shall  be  equipped  with candle 

power  incandescent  lamps  and  marine  receptacles,  in  accord- 
ance with  Drawing  No ,  dated  

attached,  also  with  oil  fonts  and  burners extra 

incandescent  lamps  shall  be  furnished. 

Electric  lights  on  signals  shall  be  arranged  on  

circuits  as  follows: 

(Distribution  and  grouping  of  lights  for  each  circuit  to  be 
shown  in  this  space.) 

SWITCHES. 
60.     General. 

Switch  mechanism  shall  perform  their  normal  operations  in 
the  following  sequence: 

1.  Unlock  switch. 

2.  Throw  switch. 

3.  Lock  switch. 

4.  Indicate. 

All  motors  in  place  shall  be  of  sufficient  capacity  and 
mechanisms  constructed  to  perform  complete  operation  of 
normal  and  reasonably  free  working  switch  in  not  more  than 
four  (4)  seconds  at  a  distance  from  interlocking  machine  of 

not  more  than ft.,  with  battery  at  ten  (10)  per  cent 

below  normal  voltage.  The  normal  voltage  of  battery  is  110. 

Note. — It    is   recommended   that    fair   working   conditions 


402  APPENDIX. 

consist  of  a  distance  of  one  thousand  (1,000)  ft.  from  inter- 
locking machine. 

Mechanisms  shall  be  so  constructed  and  equipped  that 
switch  can  be  stopped  or  reversed  at  any  point  of  movement 
by  manipulation  of  lever  controlling  same. 

Mechanism  shall  be  equipped  with  an  efficient  friction 
clutch  to  prevent  damage  to  same  in  case  movement  of 
switch  is  obstructed.  If  friction  clutch  fails  to  release  motor, 
all  parts  of  mechanism  shall  be  strong  enough  to  permit  of 
stopping  the  switch  at  any  point  of  its  movement  by  intro- 
duction of  an  obstruction  between  point  and  stock  rail  with- 
out injury  to  any  part. 

Staggered  locking  shall  be  provided  for  the  normal  and  re- 
verse position  of  the  points. 

The  hole  or  notch  in  lock  rod  shall  be  not  more  than  one- 
sixteenth  (1/16)  in.  larger  than  plunger  measured  in  a  hori- 
zontal line. 

Note. — It  is  recommended  as  a  safe  and  better  method  of 
operation  that  a  rectangular  lock  rod  be  employed  with  a 
vertical  looking  face  of  a  height  as  great  as  practicable.  Con- 
sideration should  be  given  to  the  substitution  of  better  wear- 
ing and  stronger  materials  for  those  at  present  employed  in 
the  locking  edges  and  surfaces  of  the  plunger  and  lock  rod, 
and  endeavor  should  also  be  made  to,  in  the  best  practical 
way,  secure  as  great  an  engaging  area  as  possible  when  the 
lock  rod  is  moved  three-thirty-seconds  (3/32)  in.  out  of  lock 
position. 

Switch  mechanism  shall  be  protected  by  substantial  iron 
covers  fastened  to  ties  or  mechanism  with  wrought  or  mal- 
leable iron  fastenings,  in  a  manner  to  permit  of  convenient 
inspection  of  mechanism. 

The  location  of  switch  operating  mechanism  shall  be  as 

shown  on Plan  No ,  dated 

attached. 

All  parts  of  mechanisms  and  covers  shall  be  placed  outside 

of  clearance  limits,  as  shown  on  diagram  on   Plan 

No ,  dated  ,  attached. 

61.    Mechanical  Connections. 

The  mechanical  connections  for  switch  mechanism  shall  be 
arranged  in  accordance  with  Contractor's  standard  practice, 
unless  otherwise  provided. 

Strength  of  connections  shall  be  such  that  switch  points 
can  be  stopped  by  placing  an  obstruction  between  point  and 
stock  rail  at  any  part  of  stroke  without  breaking  or  bending 
any  such  connections. 

Both  the  operating  rod  and  the  lock  rod  shall  be  of  suffi- 


APPENDIX.  403 

cient  strength  to  alone  and  independently  hold  the  switch 
points  in  position. 

Connections  shall  be  strong  enough  to  prevent  bending  or 
breaking  in  case  mechanism  is  operated  when  detector  bar  is 
engaged  by  wheels  of  a  car  or  engine. 

When  either  pipe,  pipe  joint  material,  pipe  carriers,  com- 
pensators, cranks  or  other  such  material  are  used  in  connec- 
tions between  movements  and  detector  bars,  such  material 
shall  conform  to  the  Mechanical  Interlocking  Specifications  of 
the  Eailway  Signal  Association. 

All  ties  whose  relative  location  affects  the  correct  opera- 
tion of  mechanism  shall  be  securely  strapped  together,  as 

shown   on  Purchaser's  Plan  No ,  dated    , 

attached. 

62.    Detector  Bars. 

Bars  shall  be  located  as  shown  on  Plan  No. 

,  dated ,  attached,  unless  otherwise  specified. 

Note. — Bars  on  curves  should  be  located  on  inside,  outside 
or  both  sides  of  curve,  or  as  determined  by  local  operating 
traffic  conditions. 

Detector  bars  shall  be  arranged  to  give  fifty-three  (53)  ft. 
continuous  protection  for  all  switches,  derails,  movable  wing 
and  movable  point  frogs. 

When  used  on  outside  of  rail,  detector  bar  shall  be  made 
of  one-half  by  two  and  one-quarter  (%x2:|4)  in.  wrought  iron 
or  steel,  and  have  one  beveled  edge,  square  ends  and  bolted 
joints.  Full  length  bars  shall  be  made  up  in  eighteen  (18)  ft. 
sections. 

Bars  shall  be  drilled  one  (1)  in.  from  bottom  of  bar  to  cen- 
ter of  hole  for  three  (3)  one-half  (%)  in.  countersunk  head 
bolts  or  rivets.  The  first  hole  shall  be  one  (1)  in.  from  end 
to  center  and  two  (2)  in.  between  centers  of  holes.  Where 
splice  plates  are  specified,  they  shall  be  made  of  wrought  iron 
or  steel  one-half  by  two  by  twelve  (%x2x!2)  in.,  rivetd  at 
the  end  of  bar  with  three  (3)  one-half  by  one  and  one-eighth 
(%xl^)  in.  countersunk  head  rivets  and  attached  to  inter- 
mediate adjacent  sections  by  three  (3)  one-half  by  one  and 
one-half  (%xl%)  in.  countersunk  head  bolts,  with  nuts  held 
in  place  by  nut  locks. 

Driving  pieces  shall  be  made  of  wrought  iron  or  steel  ar- 
ranged for  one  and  one-quarter  (l1^)  in.  jaw  connections. 
The  part  where  the  jaw  is  connected  shall  be  three-quarters 
by  two  by  three  (%x2x3)  in.,  and  part  riveted  to  bar  shall 
be  one-half  by  two  by  six  (^x2x6)  in.,  drilled  for  three  (3) 
one-half  (%)  in.  rivets,  one  (1)  in.  from  end  and  two  (2)  in. 
between  center  of  holes.  Offset  from  bar  to  jaw  connection 
shall  be  one  and  one-half  (1%)  in. 


404  APPENDIX. 

Driving  pieces  shall  be  placed  midway  between  two  (2) 
clips  in  space  not  occupied  by  joint,  and  the  driving  rod  shall 
have  not  more  than  seven  (7)  ft.  of  its  length  unsupported. 

Fifty-three    (53)    ft.  bars  shall  be  mounted   on   seventeen 

(17)    type  rail  clips,  and  a  proportionate  number 

of  clips  shall  be  used  for  longer  or  shorter  bars. 

Centers  of  rail  clips  shall  be  placed  eight  (8)  in.  and  twen- 
ty-six (26)  in.,  respectively,  from  ends  and  the  remaining 
clips  approximately  four  (4)  ft.  apart. 

Where  radial  arm  clips  are  used  combination  bar  stops  and 
guides  shall  be  provided  for  every  ten  (10)  ft.  of  bar  (equally 
spaced),  and  not  less  than  two  (2)  such  stops  on  one  bar. 

Bars  shall  be  mounted  substantially  and  operated  close  to 
head  of  rail  in  a  plane  inclined  toward  the  center  of  track. 

Bars  shall  rise  a  minimum  of  three-quarters  (%)  in.  above 
top  of  rail  at  every  point  before  the  unlocking  of  the  switch, 
and  shall  rest  one-quarter  (^4)  in.  below  top  of  rail  when 
lever  travel  is  completed. 

Detector  bars,  when  practicable,  shall  be  so  connected  that 
the  unlocking  movement  when  switch  is  in  the  main  line  posi- 
tion shall  be  in  the  reverse  direction  to  the  facing  movement 
of  traffic  over  the  points. 

Where  rocker  shafts  are  used,  they  shall  be  made  of  two 
(2)  in.  square  cold  rolled  steel  with  movable  bearings  and 

crank  arms.     Arms  shall  be    iron  and  nine  (9)  in. 

center  to  center.  The  bearings  shall  be  securely  bolted  to 
ties  with  four  (4)  three-quarter  (%)  in.  bolts.  The  maximum 
spacing  of  supports  shall  be  six  (6)  ft.  centers. 

Other  detector  bar  fittings,  where  required,  shall  be  Kail- 
way  Signal  Association  Standard. 

Detector    Track    Circuits. — Detector    track    circuits    will 

be  required  in  addition  to 

lieu  of 
detector  bars. 

When  detector  track  circuits  are  required,  they  shall  con- 
form to  the  following  specifications: 

Note. — Detail  specifications  to  be  given  here  for  results 
required  of  detector  track  circuits  as  to  control  of  switches, 
etc. 


Note. — Keference  is  made  in  Section  100  to  various  pur- 
poses to  which  such  circuits  may  be  applied. 
63.    Switch  Circuit  Controllers. 


APPENDIX.  405 

Circuit  controllers  of  substantial  construction  and  positive 
in  action  shall  be  provided  for  each  switch  mechanism,  and 
shall  be  so  constructed  that  they  can  be  maintained  to  make 
or  break  circuit  when  switch  point  shall  be  moved  from  the 
closed  position  three-sixteenths  (3/16)  of  an  inch. 

Operating  rods  of  switch  controllers  shall  be  one  (1)  in. 
in  diametr  and  adjustable,  with  a  maximum  distance  apart  of 
supports  of  three  (3)  ft. 

Note. — Consideration  should  be  given  to  the  question  of  the 
connection  of  the  circuit  controller  to  the  switch,  as  to 
whether  one  or  both  points  shall  be  positively  connected,  and 
if  but  one  point,  which  shall  be  selected.  It  is  recommended 
that  circuit  controller  be  insulated  from  tie  plate  and  switch 
point. 

WIRE  AND  WIRING. 

70.  Specification. 

All  wire  shall  conform  to  the  standard  specifications  of  the 
Railway  Signal  Association. 

71.  Size. 

All  wires  shall  be  of  sufficient  size  to  permit  operation  of 
switch  and  signal  mechanism  in  accordance  with  previous 
specifications. 

Rubber  covered  wire  smaller  than  No.  14  B.  &  S.  shall 

not  be  used. 

Copper  line  wire  smaller  than  No.  10  B.  &  S.  shall  not 
be  used. 

72.  Tagging. 

All  wires  shall  be  tagged  at  all  junction  boxes,  switches, 
signals,  relay  boxes,  arrester  boxes  and  at  all  line  wire  con- 
nections. 

All  tags  shall  be  made  of  vulcanized  sheet  fiber  not  less 
than  one-sixteenth  (1-16)  in.  thick,  firmly  attached  to  the 
wire  by  best  quality  tarred  yacht  marline  one-sixteenth  (1-16) 
in.  in  diameter. 

The  tag  shall  have  a  stamped  imprint  to  show  the  functions 
of  the  wire. 

73.  Runs. 

Wires  shall  be  laid  loosely  in  trunking  without  stretching 
or  crowding. 

All  wires  shall,  as  far  as  practicable,  be  continuous  without 
joints  or  breaks  between  interlocking  machine  and  the  unit 
operated;  joints  when  made  shall  be  in  junction  boxes  and 
only  made  on  permission  from  Supervisor. 

In  submarine  cable  work  spare  wires  up  to  twenty-five  (25) 
per  cent  of  the  number  in  use  shall  be  provided  as  specified. 
When  spare  wires  are  required  in  other  than  cable  work  the 
number  and  size  shall  be  specified. 


406  APPENDIX. 

74.  Common. 

Unless  otherwise  specified,  common  wires  shall  be  continu- 
ous without  joints  or  breaks  from  interlocking  machine  to  the 
limits  of  the  interlocking  plant. 

Seductions  in  size  of  common  wire  and  connections  to  pole 
lines  shall  be  made  in  junction  boxes. 

All  connections  between  branches  and  main  common  wires 
shall  be  made  in  junction  boxes,  with  combination  clamps  and 
terminals  mounted  on  slate  bases. 

But  one  unit  shall  be  connected  to  one  branch  from  the 
common  wire. 

No  common  wire  shall  be  less  than  No.  12  B.  &  S.  gage. 

75.  Joints. 

Joints  must  be  made  as  follows: 

Braid  shall  be  pulled  back  one  (1)  in.  from  end  of  rubber 
on  each  side  of  splice,  and  rubber  cut  with  knife  held  at  an 
angle  of  approximately  thirty  degrees  with  axis  of  wire,  as 
one  would  sharpen  a  pencil. 

After  removing  rubber,  wire  shall  be  thoroughly  cleaned, 
care  being  taken  to  prevent  injury  from  small  cuts  or  nicks. 

Wire,  after  being  cleaned,  will  be  twisted  together  in  the 
form  of  a  regular  line  wire  splice,  turns  being  spaced  approxi- 
mately one-sixty-fourth  (1-64)  in. 

Joints  shall  then  be  soldered  by  pouring  on,  or  dipping 
wire  into,  melted  solder,  a  non-corrosive  rosin  flux  being  used. 
After  soldering,  joints  shall  be  painted  with  in- 
sulating paint  or  with  compound.  Joints  will 

then  be  covered  with  two  layers  of insulating  tape 

between  ends  of  braid,  which  tape  shall  be  heated  sufficiently 
to  form  a  tight  covering  but  not  enough  to  injure  the  quality 

of  the  material.  Coating  of insulating  paint  or 

compound  shall  be  put  on  over  insulating  tape  and 

two  layers  of  adhesive  or  friction  tape  shall  be 

applied,  after  which  the  outside  of  joint  is  to  be  painted  with 
insulating  paint. 

WIEE  PBOTECTION. 

80.    Trunking  and  Conduit. 

Trunking,  when  on  stakes  above  ground  and  running  par- 
allel with  the  track,  shall  not  be  placed  nearer  than  six  (6) 
ft.  from  the  gage  side  of  the  nearest  rail  except  by  special 
permission. 

Local  conditions  shall  determine  the  height  of  trunking 
when  above  ground;  in  general,  when  trunking  is  run  parallel 
with  the  tracks,  bottom  of  trunking  shall  be  placed  approxi- 
mately six  (6)  in.  above  the  ground. 


APPENDIX.  407 

The  location  of  the  main  runs  of  trunking  is  shown  on 
Plan  No ,  dated ,  attached. 

Note. — Permission  should  be  obtained  to  place  between 
tracks  run  of  trunking  parallel  with  the  tracks. 

Material. — All  grooved  trunking,  built  up  trunking  and  all 
capping,  as  specified,  shall  be  made  in  accordance  with  Kail- 
way  Signal  Association  drawings  for  standard  wood  trunking, 
dated  July  8,  1908. 

Commercial  sizes  of  lumber  shall  be  used,  finished  on  one 
side  and  two  edges. 

Where  slight  changes  in  dimensions  of  grooved  or  built  up 
trunking  are  necessary,  either  due  to  failure  of  the  commer- 
cial lumber  to  run  to  exact  sizes  or  due  to  finishing  of  the 
surfaces,  such  changes  shall  be  allowed  for  in  the  walls  of 
groove,  the  groove  remaining  exact  size  throughout. 

As  specified,  capping  shall  be  securely  fastened  to  trunking 

with 

gate  hooks, 
nails. 

Note. — It  is  recommended  that  gate  hooks  be  used  on  main 
runs  of  trunking  and  nails  on  cross  leads. 

Nails  shall  not  be  driven  through  the  trunking  from  the 
inside  of  the  groove  nor  shall  they  be  driven  into  the  groove 
from  the  inside. 

Drainage  of  the  trunking  shall  be  provided  as  follows: 


Inside  corner  of  trunking,  at  turns,  must  be  rounded  to 
prevent  insulation  on  wires  being  injured. 

Not  less  than  one-third  (%)  of  the  capacity  of  the  groove 
shall  remain  free  for  the  further  installation  of  wires. 

Surfaces  of  trunking  that  are  to  be  painted  shall  be  fin- 
ished. 

Treated  trunking  must  be  used  when  specified,  and  shall 
comply  with  the  requirements  as  to  treatment  which  are 
attached  . 


When  specified,  the  wires  in  the  trunking  shall  be  loosely 
bound  and  shall  be  so  laid  in  pitch  as  to  be  practically  free 
of  contact  with  all  walls  of  the  trunking.  Pitch  as  used  must 
not  crack  at  a  temperature  of  ....  degres  F.,  and  must  not 

melt  at  a  temperature  of    degrees  F.     It  must  neither 

contain  any  material  nor  be  applied  at  a  temperature  which 
will  injure  the  rubber  insulation. 


408  APPENDIX. 

Boot-Legs. — Boot-legs  for  track  connections  shall  be  made 

according  to   Plan  No ,  dated   

t   attached,   and   shall  be   securely    fastened   to   the 

trunking  not  less  than  two    (2)    in.  from  base  of  rail,  and 
shall  not  extend  more  than  one  (1)  in.  above  base  of  rail. 

Joints. — Except  as  otherwise  shown  in  drawings  which 
have  been  furnished,  all  joints  in  grooved  trunking  shall  be 
lapped,  the  ends  of  trunking  being  beveled  at  an  angle  of 
forty-five  (45)  degrees. 

When  trunking  is  built  up  all  joints  shall  be  staggered. 

All  joints  in  capping  shall  be  made  at  least  one   (1)   ft. 
from  joints   in   trunking. 
81. — Supports. 

Trunking  above  ground  shall  be  supported  on  stakes  placed 
not  more  than  five  (5)  ft.  centers. 

Except  as  shown  on  attached  drawings,  stakes  shall  be 
made  three  (3)  in.  by  four  (4)  in.,  or  of  equiva- 
lent circular  section,  and  of  sufficient  length  to  allow  them 
to  be  placed  at  least  two  (2)  ft.  in  the  ground.  When,  due 
to  local  requirements,  such  as  contour  of  the  ground  or  other 
physical  conditions,  stakes  of  a  greater  length  than  three  (3) 
ft.  six  (6)  in.,  or  a  greater  cross-section  than  three  (3)  in. 
by  four  (4)  in.  will  be  necessary,  information  as  to  the  num- 
ber, length  and  cross-section  of  such  will  be  furnished  by  the 
Purchaser  to  the  Contractor. 

All  stakes  supporting  trunking  shall  be  placed  vertically 
and  extend  at  least  two  (2)  ft.  below  the  surface  of  the 
ground,  unless  otherwise  specified. 

A  piece  of  capping  eight  (8)  in.  long  and  the  width  of  the 
trunking  shall  be  placed  between  the  trunking  and  each 
stake. 

All  joints  in  the  bottom  of  the  trunking  shall  be  supported 
by  stakes. 

Where  trunking  exceeds  a  width  of  seven  (7)  in.  a  special 
arrangement  consisting  of  (a  double  line  of  stakes — a  single 
line  of  large)  stakes  shall  be  installed,  or  provision  shall  be 
made  as  follows.. 


82.    Junction  Boxes. 

Location. — Junction  boxes  shall  be  located  as  shown  on 

Plan  No ,  dated ,  attached 

(which  also  shows  general  runs  of  trunking),  and  at  a  height 
sufficient  to  allow  terminals  to  be  placed  at  least  six  (6)  in. 
above  top  of  trunking. 

When  so  indicated  on  plan,  junction  boxes  shall  be  sup- 
ported in  the  same  manner  as  the  trunking. 


APPENDIX.  409 

Material. — Junction  boxes  shall  be  made  of  

and  so  designed  that  terminals  will  be  kept  dry.  Each  junc- 
tion box  shall  be  fitted  with  a  cover,  hasp  and  staple  suit- 
able for  the  Purchaser's  standard  lock,  No ,  made 

by 

Size. — Where  ten  (10)  or  less  wires  are  used,  junction 
boxes  shall  be  sixteen  (16)  in.  square  by  twenty  (20)  in. 
deep  inside  dimensions,  and  shall  be  increased  six  (6)  in.  in 
length  for  each  ten  (10)  or  fraction  thereof  additional  con- 
nections made  in  the  box. 

83.  Lightning  Arresters. 

Lightning  arresters  of  design  shall  be  used  at 

all  aerial  line  connections. 

Lightning  arresters  shall  be  grounded  through  two  (2)  No. 
8  B.  &  S.  gage  copper  wires  (insulated  above  ground), 
wrapped  around  and  soldered  to  a  galvanized  iron  ground  rod 
not  less  than  one  (1)  in.  in  diameter,  driven  eight  (8)  ft. 
into  the  ground. 

Where  such  ground  connection  is  not  satisfactory  the  de- 
sired protection  for  each  point  shall  be  specified  by  the  Pur- 
chaser and  furnished  in  place  by  the 

84.  Fuses. 

The  necessary  fuses  to  properly  protect  all  apparatus  and 
circuits  shall  be  installed. 

Double  pole  fuse  cut-out  shall  be  provided  for  each  circuit 
on  power  board. 

An  additional  double  fuse  cut-out  shall  be  placed  in  stor- 
age battery  leads  as  near  as  possible  to  battery  terminals. 
CIRCUITS. 

90.  General. 

All  circuits  shall  conform  to  the  Contractor's  recommended 
practice  unless  otherwise  specified. 

91.  Signals. 

All  high  and  intermediate  speed  signals  shall  be  so  con- 
trolled by  circuit  breakers  on  all  facing  derail,  switch  and 
frog  points  over  which  they  govern,  that  unless  such  points 
are  in  proper  position  and  locked  the  signals  will  assume  the 
stop  position.  Low  speed  signals  shall  be  controlled  by 
facing  point  derails  in  the  same  manner. 

Each  distant  signal  shall  be  controlled  by  circuit  breakers 
on  all  signals,  the  indication  of  which  it  repeats,  and  so  ar- 
ranged that  the  circuit  to  the  distant  signal  is  broken  unless 
all  signals  for  the  track  governed  are  in  proceed  position. 

All  non-interlocked  single  main  line  switches,  both  ends  of 
cross-over  switches  and  siding  derails  between  home  and  dis- 
tant signals  shall  be  protected  by  switch  circuit  controllers. 

92.  Switches. 


410  APPENDIX. 

The  circuits  for  facing  point  derails  shall  be  controlled  by 
normally  closed  circuit  breakers  on  all  signals  governing  over 
them. 

93.  Cross  Protection. 

Protective  circuits  shall  be  so  arranged  as  to: 

(a)  Automatically  disconnect  any  unit  or  units  improp- 
erly supplied  with  power. 

(b)  Prevent  the  restoration  of  power  until  the  trouble  is 
removed. 

(c)  Cause  an  operative  failure  in  event  of  any  failure  in 
the  protective  circuit. 

94.  Switchboard, 

The  Contractor's  recommended  arrangement  of  circuits 
shall  be  followed,  subject  to  necessary  modification  on  ac- 
count of  special  requirements. 

95.  Electric  Lighting. 

96.  Special. 

Note.  —  The  Purchaser  will  here  indicate  in  full  detail  all 
special  circuit  requirements. 

(a)  .................................................... 

(b)  .................................................... 

(c)  .................................................  ... 

(a; 


TEACK  CIRCUITS. 

100.  General. 

The   Contractor   shall   provide    ........    track   circuits   as 

shown  by  the  shaded  tracks  on  Purchaser's  plans.     The  pur- 

pose or  purposes  of  each  track  circuit  will  be  indicated  on 

the  plan  by  one  (1)  or  more  of  the  following  letters: 

Number. 

S  ............  for  control  of  semi-automatic  signals. 

D  ............  in  place  of  or  in  addition  to  detector  bars. 

F  ............  for  control  of  fouling  point  indicators. 

A  ............  for  control  of  annunciators. 

B  ............  for  control  of  route  locks. 

B  ............  for  control  of  automatic  block  signals. 

C  ............  for  control  of  highway  crossing  bells. 

All  sidings  and  siding  crossovers  shall  be  protected  by 
shunt  track  sections  extending  to  the  fouling  point  of  derail; 
main  line  crossovers  shall  be  protected  by  as  much  shunt 
track  section  as  can  be  obtained. 

101.  Bonding. 

All  rail  joints,  except  as  mentioned  below,  shall  be  bonded 
with  two  (2)  No.  8  W.  &  M.  gage  (162  in.  diameter)  E.  B. 
B.  galvanized  iron  wires  ........  in.  long. 


APPENDIX.  411 

Note. — There  should  be  a  specification  submitted  covering 
the  manufacture  of  the  material  in  the  bond  wires. 

Bond  wires  shall  be  located  outside  of  splices  and  at  least 
one  wire  shall  be  on  gage  side  of  rails. 

Each  bond  wire  shall  be  fastened  at  each  end  into  the  web 
of  the  rail  by  a  channel  pin  or  bonding  tube. 

Bonding  shall  be  completed  on  the  same  day  that  holes  are 
drilled. 

Note. — It  is  recommended  that  No.  6  B.  &  S.  gage  bare 
copper  or  copper-clad  bond  wires  shall  be  used  in  tunnels  and 
applied  as  above  mentioned. 

It  is  recommended  that  at  joints  in  highway  and  street 
crossings  and  in  station  platforms  that  two  iron  or  copper- 
clad  bond  wires  shall  be  used  on  gage  side  of  rail  and  two 
copper  or  copper  clad  wires  on  outside  of  rail  and  applied  as 
above  mentioned. 

Frogs  shall  be  bonded  in  the  same  manner  as  rail  joints 
and  shall  be  so  connected  that  the  continuity  of  the  track 
circuit  will  be  broken  when  they  are  taken  from  the  track. 

Pins  or  tubes  shall  be  made  of  iron  or  steel  coated  with 
copper  or  tin  and  shall  be  of  such  length,  shape  and  hardness 
that  when  driven  into  the  rail  in  combination  with  the  bond 
wire  they  will  completely  fill  in  cross-section  a  nine-thirty- 
second  (9-32)  in.  hole  in  web  of  rail  and  will  form  a  good 
mechanical  and  electrical  connection. 

The  following  types  of  channel  pins  or  bonding  tubes  are 
satisfactory  to  the  Purchaser 

Pins  or  tubes  will  be  calibrated  by  the  Purchaser. 

A  selection  will  be  made  from  each  package  of  pins  for 
test. 

A  variation  of  the  thickness  of  the  pin  or  tube  between 
the  base  of  the  groove  at  the  center  and  the  outer  wall 
greater  than  one-sixty-fourth  (1-64)  in.  will  not  be  permit- 
ted, or  else  a  variation  either  way  from  the  outside  diam- 
eter of  the  standard  pin  or  tube  at  center  greater  than  one 
one-hundred-twenty-eighth  (1-128)  in.  will  not  be  permitted. 

The  entire  shipment  will  be  rejected  should  five   (5)   per 
cent  of  the  pins  or  tubes  tested  prove  defective. 
102.    Insulated  Joints. 

Insulated  rail  joints  shall  be  furnished  by  the  Purchaser 
and  installed  by  the  Purchaser  at  joints  designated  by  the 
Contractor. 

Insulations  for  bridle  rods  shall  be  furnished  by  the   .... 

and  installed  by  the  Purchaser  at  points  designated 

by  the  Contractor. 


412  APPENDIX. 

Insulated  tie  plates  and  other  insulated  interlocking  con- 
nections shall  be  furnished  and  installed  by  the  

Both  rails  shall  be  insulated  at  fouling  points,  ends  of 
track  circuits  and  in  switch  leads. 

All  rail  joints  to  be  insulated  are  Ibs 

section,  as  shown  on  attached  drawings,  and  as  located  on 
plan  of  tracks. 

All  switches  to  be  insulated  are  equipped  with 

bridle  rods  in.  by in.  cross-section, 

as  shown  on  attached  drawings,  except  as  noted  on  plan  of 
tracks. 

103.  Track  Battery. 

Each  track  circuit  shall  be  operated  by  at  least  two  (2) 
cells  of  gravity  battery  connected  in  multiple. 

Jars  shall  be  of  glass,  six  (6)  in.  in  diameter  by  eight  (8) 
in.  in  height  by  one-eighth  (%)  in.  thick. 

Zincs  shall  be  four  (4)  Ibs.,  circular,  amalgamated,  with 
two  (2)  per  cent  mercury  supplied  with  brass  terminal  and 
suspended  from  three  points;  unless  other  types  are  specified. 

Coppers  shall  be  flat  leaf  with  connecting  wire  riveted, 
and  shall  be  so  shaped  that  they  will  be  held  in  place  by  the 
copper  sulphate. 

Three  (3)  Ibs.  of  good  copper  sulphate,  free  from  dust, 
shall  be  furnished  with  each  cell. 

Note. — Complete  specifications  for  battery  materials  should 
be  furnished  by  Purchaser,  if  practicable. 

104.  Battery  Housing. 

Unless  otherwise  specified,  track  batteries  shall  be  housed 

in  three  (3)  cell  chutes ft.  deep,  as  per 

cast  iron 

concrete 

drawing  attached,  weighing  for  cast  iron  not  less  than  three 

hundred  (300)  Ibs.  each.     Each  chute  shall  be  provided  with 

a  three  (3)  cell  elevator,  rope,  and  if  specified,  a  frost  board. 

105.  Relays. 

Eelays  shall  conform  to  specifications  of  the  Eailway  Sig- 
nal Association  dated  October,  1906. 

106.  Belay  Housing. 

When  possible,  relays  shall  be  housed  in  the  signal  mechan- 
ism case;    otherwise   they   shall   be   housed  in  weatherproof 
iron 
wood 

boxes  located  as  specified,  in  the  tower,  on  signal 
bridges  or  on  posts, 

iron 
wood 


APPENDIX.  413 

107.  Switch  Protection  for  Non-Interlocked  Switches. 

Circuit  controllers  for  non-interlocked  switches  shall  have 
two  independent  shunt  connections  to  the  track  circuit  of 
each  track  made  dangerous  by  the  opening  of  switch.  Switch 
circuit  controllers  shall  be  located  on  the  same  side  of  switch 
as  the  normally  closed  point  and  connected  thereto,  and  shall 
be  arranged  to  shunt  track  circuits  when  point  is  open  one- 
quarter  (}4)  in.  or  more. 

108.  Connections. 

Track  batteries  and  relays  shall  be  connected  to  the  rails 
by  single  conductor  B.  &  S.  gage,  rubber  covered, 

No.  8 
No.  10 

soft  drawn  copper  wire.  Fouling  shunt  connections  and 
switch  box  shunt  connections  shall  be  made  with  two  single 
conductor  B.  &  S.  Gage,  rubber  covered,  soft 

No.  8 
No.  10 
drawn  copper  wire. 

Rubber  covered  stranded  wire  of B.  &  S.  gage 

shall  be  used  from  trunking  to  track  batteries  when  track 
batteries  are  in  chutes. 

Note. — A  minimum  gage  of  No.  12  B.  &  S.  is  recommended 
for  such  wire. 

PAINTING. 

110.  General. 

All  materials  shall  be  pure  and  the  quality  of  paint  shall 
be  such  as  will  permit  of  the  application  herein  specified. 

111.  Cleaning. 

Surfaces  covered  with  rust,  grease,  dirt  or  other  foreign 
substances,  shall  be  thoroughly  cleaned  by  scraping  or  other 
suitable  method  before  paint  or  oil  is  applied. 

112.  Mixing. 

113.  Application. 

General. — Paint  shall  not  be  applied  to  outside  surfaces  in 
wet  weather,  nor  shall  any  surface  be  painted  until  it  is 
cleaned  and  dried,  nor  until  previous  coating  has  thoroughly 
dried. 

Pigment  finishing  coats  shall  be  of  sufficient  body  to  form 
an  opaque  coating. 

Finishing  coats  shall  not  be  applied  sooner  than  forty- 
eight  (48)  hours  after  the  previous  coating  has  been  applied. 

Paints  mixed  on  the  ground  shall  be  applied  within  three 
(3)  hours  after  the  pigment  and  oil  are  mixed. 

All  priming  coats  shall  be  applied  as  soon  as  is  consistent 
with  the  progress  of  the  work. 

All  second  coatings  shall  be  applied  in  sufficient  time  for 


414  APPENDIX. 

the  third  coat  to  be  applied  and  dry  when  the  plant  is  com- 
pleted. 

Iron  Work. — All  iron  work,  except  detector  bars  and  fin- 
ished parts  of  machine,  shall  be  given  one  priming  of  red 
lead  and  raw  linseed  oil  and  two  (2)  finishing  coats. 

The  following  specific  finishing  coats  shall  be  used: 

Kind  of  Paint.     Color. 

Signal  bridges  and  brackets 

Signal   masts 

Switch  mechanisms  and  connections 

Wood  Work. — Exposed  wood  work  shall  be  given  one  prim- 
ing coat  and  finishing  coats  as  follows: 

Kind  Number 

Paint.  Color.         Coats. 

Home  signal  blades 

Dwarf   signal   blades 

Distant  signal  blades 

Trunking,     junction     boxes, 

etc 

114.    Buildings. 

All  towers  or  other  buildings  in  connection  with  the  inter- 
locking plant,  if  built  of  wood,  shall  receive  one  priming 
coat  and  two  finishing  coats  as  specified  below. 

The  priming  coat  shall  consist  of   ,  and,  when 

thoroughly  dry,  two  coats  of  pure  lead  and  oil,  in  the  fol- 
lowing tints,  shall  be  applied: 


Prepared  paints  manufactured  by. 


will  be  accepted. 
120.     Special. 

SUPPLEMENTARY  SPECIFICATIONS  FOE  DEAW- 
BEIDGES. 

130.    Locking. 

At  least  one  lever  of  the  interlocking  machine,  called  the 
bridge  lock  lever,  shall  be  assigned  for  the  purpose  of  lock- 
ing the  bridge.  The  bridge  lock  lever,  when  reversed,  shall 
be  arranged  to  lock  the  bridge  in  the  closed  position  and  to 
prevent  the  application  of  power  for  the  purpose  of  with- 
drawing the  bridge  latch  or  opening  the  bridge. 

The  bridge  lock  lever,  when  normal,  shall  be  arranged  to 
lock  all  levers  used  for  bridge  protection  in  the  proper  posi- 


APPENDIX.  415 

tion  to  protect  the  bridge,  and  also  to  cut  off  power  from  all 
control  wires  leading  to  such  functions. 

A  separate  locking  arrangement  shall  be  provided  for  each 
of  the  following  purposes: 

(a)  To  insure  that  the  bridge  is  in  proper  alinement. 

(b)  To   insure   that  all  bridge   surfacing  devices  are  in 
their  proper  position. 

(c)  To  lock  all  rails  in  proper  position  for  train  move- 
ment. 

The  Purchaser  will  supply  complete  information,  including 
detail  drawings,  of  bridge  locking  apparatus  to  be  controlled 
by  the  interlocking  machine. 

Note. — It  is  recommended  as  a  more  desirable  method  of 
operation  that  the  fails  at  the  end  of  the  draw  and  on  the 
shore  next  to  the  draw  be  fixed  in  position  and  have  the 
necessary  locks,  and  that  lifting  rails  be  not  used. 

THE  END. 


OF  THE 

UNIVERSITY 

OF 


INDEX 


A. 

Adjustments — Special  Switch  92 

Alarms — Highway    8,  313 

Ampere   134 

Annunciators 8,  313 

Arms — Radial    79 

Armature 58 

Arresters — Lightning 268 

B. 

Back  Light  Casting 102 

Back  Locking 249 

Bars — Crossing    251 

Bars— Deflecting 69,  70,  79 

Bars — Detector    94 

Bars — Vertical  Deflecting. 69,  70 
Bars — Slide  for  Switch  and 

Lock  Movement 97 

Battery 56 

Battery  Cell 56 

Battery— Dry 292 

Battery— Gravity  Cell 131 

Battery — In  Series 164 

Battery — Lalande   132 

Battery — Poles  of 57 

Battery — Primary  Cell 131 

Battery — Storage    133 

Bearing — Arm  Plate 102 

Block — Definition  of 278 

Block— Manual 278 

Block — Telegraph    278 

Blocking— Absolute 279 

Blocking — Controlled    Man- 
ual   13,  382 

Blocking — Permissive 279 

Blocks — Plunger    93 

Bolt  Locks    95,  104 

Bolt  Locks — Wire  Connect- 
ed     109 

Boxes — Junction 163,  209 

Boxes — Stuffing  Pipe 128 

Boxes — Stuffing  Wire 128 

Boxes — Switch 299 

Burner — Long  Time 277 

C. 

Cable— Wire    209 

Casting— Back  Light 102 


Page  Page 

Castings — Plunger    93 

Casting — Spectacle   101 

Carriers — Pipe 74 

Carriers — Pipe   Transverse.  74 
Carriers  —  Pipe  —  Special 

Wrought 77 

Carriers— Wire    77 

Chain— Use  of 73 

Chart — Dog    215 

Chart— Locking 212 

Chart — Manipulation    243 

Circuit— Track 13,  257 

Circuits — Detector    200 

Circuits — Grounded 292 

Compensators — Lazy    Jack.  82 

Compensators — Spacing  of.  18 
Compensators —  S  t  ra  i  g  h  t 

Arm 82 

Compensators — Wire 87 

Compressor — Air 139 

Coupler— Bridge    123 

Contract — Joint — Draft  of.  232 
Contract — Junior     road    to 

pay  an — Draft  of 330 

Crank — Escapement   96 

Cranks — Acute  Angle 79 

Cranks — Horizontal    71 

Cranks— "L"    102 

Cranks — Obtuse  Angle  ....  79 

Cranks — Right  Angle 79 

Cranks — Vertical    69,  70 

Crossings — Movable   Point..  100 

Cross  Locks   37 

Currents — Alternating 193 

Current — Divisibility  of 156 

Cylinders — Switch — Electro- 
pneumatic  145 

D. 

Derailing  Switches 34 

Derails 34,  119 

Derails— Solid   119 

Derails— Split  Point 119 

Derails— Wharton   119 

Drainage 127 

Drawbridges — Compensation. 

of 125 

Dynamo    132 


417 


418 


INDEX 


E. 


Page 


Electro      Motive      Force  — 

Counter   132,  181 

Estimates — Automatic     Sig- 
nals     342 

Estimates — Mechanical     In- 
terlocking    336 

Estimates  —  Power      Inter- 
locking      341 

Foundations — Compensator.  88 

Foundations — Crank 88 

Foundations — Pipe    Carrier.  75 

Function 320 

Fuses 184 

G. 

Generator — Electric    132 

Ground — Rods   268 

I. 

Indication — Dynamic    182 

Indication — Locking    56,   64 

Indication — Signal    153 

Indication  —  Switch — Elec- 
tro-pneumatic     140 

Indication— U.   S.   &  S.   All 

Electric 193 

Indication— Night    14,  272 

Indicators 312 

Induction  Coil 205 

Interlocking    11,   34 

Interlocking — All    Electric . 

.. 63,  174 

Interlocking — Definition  of.      35 
Interlocking  —  Division     of 

cost  of    319 

Interlocking — Drawbridge   .    122 
Interlocking —  Electro-pneu- 
matic     139 

Interlocking — Low  pressure 

pneumatic 166 

Interlocking  —  Maintenance 

of 318 

Interlocking  Machine 36 

Interlocking  Machine — Elec- 
tro-pneumatic     140 

Interlocking  Machine — Hor- 
izontal Leadout 74 

Interlocking    Machine — Me- 
chanical         47 

Interlocking  Machine — Sax- 

by  and  Farmer 39 

Interlocking    Machine — Ste- 
vens      47 

Interlocking  Machine — Ver- 
tical Locking 45 

Interlocking — Operation  of.   319 

Interlocking — Power 56 

Interlocking — Power  —  Sax- 
by  and  Farmer  Type ....     59 


J. 


Page 


Jaws— Double    125 

Jaws — Gain  Stroke 119 

Jaws — Offsets  in 86 

Jaws — Screw  . . , 85,  102 

Jaws — Solid   66 

Jaws — Stub  end    124 

Jaws — Wide   125 

Joints — Insulated — use  of..  257 

Joints — Wire    210 


Lamp — C.  &  N.  W.  Distant 

Signal  275 

Lamps — Semaphore 274 

Leadouts  71 

Legal  Requirements  335 

Levers — Numbering  of  ....  235 

Levers — Painting  of 245 

Lightning  Arresters  268 

Lock  and  Block 284 

Lock — Bolt  95,  104 

Lock — Bolt  Wire  Connected  109 

Lock— Electric 249 

Lock— Electric  Switch 283 

Lock — Facing  Point 94 

Lock — Time  254 

Locking — Back  249 

Locking — Bars  37 

Locking— Bed  34 

Locking — Dogs 36 

Locking — Electric  257 

Locking — Horizontal 36 

Locking  —  Preliminary  o  r 

Latch 44 

Locking— Special 214 

Locking — Special  Saxby  and 

Farmer  49 

Locking  —  Special  Vertical 

Type  53 

Locking — Vertical  36 

Long  Time  Burners 277 

Lugs— Point 92 

M. 

Machine  —  Interlocking  — 

Amer.  Ry.  Sig.  Co 203 

Machine  —  Interlocking  — 

Federal  Ry.  Sig.  Co 202 

Movements  —  Signal —  Gen. 

Ry.  Sig.  Co 185,  189 

Machine  —  Interlocking  U. 

S.  &  S.  Co.— All  Electric.  192 
Machine  —  Switch  —  Amer. 

Ry.  Sig.  Co 206 

Machine — Switch — Gen.  Ry. 

Sig.  Co 177 

Machine — Switch,  U.  S.  & 

S.  Co.  All  Electric 194 

Machines — Torpedo 120 


INDEX 


419 


Page 

Magnets    57 

Magnets — Artificial 57 

Magnets — Electro    58 

Magnets — Indication   ...60,  177 

Magnets— Safety   182 

Model— Track    161 

Motor — Electric 132 

Movements  —  Switch     and 

Lock    96 

Movements  —  Switch     and 

Lock — Tandem 160 

Movements — Switch —  Elec- 
tro-pneumatic       150 

O. 

Overlap   301 

P. 

Pipe— Galvanized    127 

Pipe — Joints  in 68 

Pipe — plugs 68 

Pipe — Signal    66 

Pipe — Underground 128 

Plans— Track 16 

Plate— Arm    101 

Plates — Tie    95 

Plunger    for    facing    point 

lock   93 

Poles— Bracket 32 

Positions — Normal    39 

Positions — Reversed   39 

Posts— Binding    136 

Power  Boards   191 

R. 

Relays 204 

Relays — Interlocking    264 

Relays — Polarized 310 

Relays — Stick 263 

Release — Hand    262 

Resistance — Electrical    135 

Rod— Eye 102 

Rods — Front    92 

Rods — Ground 268 

Rods— Lock    93 

Roundels 274 

S. 

Screws — Adjusting   85 

Screws — Wire  Adjusting  . .  110 

Segments — Indication 61 

Selectors   113 

Selector — Indication 183 

Selectors — Pipe 113 

Selectors — Wire 115 

Shafts— Rocking    69,   70 

Sheets — Dog 215 

Sheets — Locking    212 

Signal — Amer.  Ry.  Sig.  Co.  297 

Signal — Audible  Fixed. ....  8 

Signal — Fixed 7 


Page 

Signal — Automatic 12,  294 

Signal  —  Automatic —  Loca- 
tion of   298 

Signal— Base   101 

Signal — Blade    11 

Signal— Block 8,  12 

Signal— Definition    7 

Signal — Distant 9 

Signal — Dwarf    18,  103 

Signal — Dwarf  —  Gen.     Ry. 

Sig.  Co.'s    190 

Signal— Gas    247,  297 

Signal — Enclosed  Disc  ....  295 
Signal— Fed.  Ry.  Sig.  Co..  297 

Signal — Gen.  Elec.  Co 297 

Signal — Gen.  Ry.  Sig.  Co.'s 

Model  5    297 

Signal — Hall  Sig.  Co 297 

Signal— High 103 

Signal — High  —  Amer.     Ry. 

Sig.  Co 207 

Signal— High— U.    S.    &    S. 

Co.   All   Electric 195 

Signal — Home    9 

Signal — Manual 12 

Signal— Pole    101 

Signal— Pot   27 

Signal — Route   12 

Signal — Semaphore 8,  9 

Signal — Three  Position.... 

11,  27,  302 

Signal— Train  Order 8,  14 

Signal— Two  Position 22 

Signal — Upper  Quadrant. . .  29 
Signal — Union — Style  B . . .  297 
Signal— Visual  Fixed  ...8,  278 
Signal — Alternating  Current  314 
Signals — Automatic  Block — 

Single  Track    302 

Signals  —  Automatic  —  Cir- 
cuits for 304 

Signals  —  Automatic  —  Re- 
marks on    350 

Signals— Bracket 110 

Signals — General  Principles 

of 343 

Signals  —  Manual    Block  — 

Remarks  on 353 

Signals  —  Normal      Danger 

Automatic 303 

Signals — Normal   Clear  Au- 
tomatic      303 

Signals — Pipe  Connected. ..   101 

Signals — Placing  of 29 

Signals — Power  Distant...  247 
Signals — Switch  Protection.  270 
Signals — Wire  Connected.. 

72,  107 

Signal     Engineer  —  Depart- 
ment to  which  he  belongs  355 


420 


INDEX 


Page 
Signal      Movements  —  Gen. 

By.  Sig.  Co 185,  189 

Solenoids 190 

Slots— Electric    292 

Slots — Mechanical 116 

Spacing  of  levers  and  cranks     80 

Specifications 356 

Spindle   302 

Staff  Block  System 13,  284 

Stakes 78 

Stops — Automatic  Train...   334 
Switch     and     Lock     Move- 
ments       96 

Switch  Boxes 299 

Switch   Machine — Gen.    Ry. 

Sig.  Co 177 

Switches — Operation   of 91 

Switches — Slip  —  Operation 

of 98 

T. 

Timbers— Special    Switch..   100 
Tops — Pipe  Carrier 75 


Page 

Torpedo  Machine 8,  120 

Towers — Interlocking  .....    355 

Transformers 192 

Trunking 162 

TJ. 
Unit — Operated 320 

V. 

Valves — Relay   .   167 

Volt 134 

W. 

Watt— Definition  of 174 

Wheels— Chain— Tandem  ..  107 

Wheels — Chain — Vertical    .  73 

Wire — Insulated 57 

Wire — Line  . : 314 

Wire — Rubber  Covered  162 

Wire— Signal   209 

Wire — Weather  Proof 314 


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